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  (adapted from Commodore 64 Programmer's Reference Guide from Project 64)

  Link: Project 64 Page


  This chapter explains CBM BASIC Language keywords. First we give you an

  easy to read list of keywords, their abbreviations and what each letter

  looks like on the screen. Then we explain how the syntax and operation of

  each keyword works in detail, and examples are shown to give you an idea

  as to how to use them in your programs.

    As a convenience, Commodore PET BASIC allows you to abbreviate most

  keywords. Abbreviations are entered by typing enough letters of the

  keyword to distinguish it from all other keywords, with the last letter

  or graphics entered holding down the [SHIFT] key.

    Abbreviations do NOT save any memory when they're used in programs,

  because all keywords are reduced to single-character "tokens" by the

  BASIC Interpreter. When a program containing abbreviations is listed, all

  keywords appear in their fully spelled form. You can use abbreviations to

  put more statements onto a program line even if they won't fit onto the

  80-character logical screen line. The Screen Editor works on an 80-

  character line. This means that if you use abbreviations on any line that

  goes over 80 characters, you will NOT be able to edit that line when

  LISTed. Instead, what you'll have to do is (1) retype the entire line

  including all abbreviations, or (2) break the single line of code into

  two lines, each with its own line number, etc.

    A complete list of keywords, abbreviations, and their appearance on the

  screen is presented in Table 2-1. They are followed by an alphabetical

  description of all the statements, commands, and functions available on

  your Commodore PET.

    This chapter also explains the BASIC functions built into the BASIC

  Language Interpreter. Built-in functions can be used in direct mode

  statements or in any program, without having to define the function

  further. This is NOT the case with user-defined functions. The results of

  built-in BASIC functions can be used as immediate output or they can be

  assigned to a variable name of an appropriate type. There are two types

  of BASIC functions:

    1) NUMERIC

    2) STRING

    Arguments of built-in functions are always enclosed in parentheses ().

  The parentheses always come directly after the function keyword and NO

  SPACES between the last letter of the keyword and the left parenthesis (.

    The type of argument needed is generally decided by the data type in

  the result. Functions which return a string value as their result are

  identified by having a dollar sign ($) as the last character of the

  keyword. In some cases string functions contain one or more numeric

  argument. Numeric functions will convert between integer and floating-

  point format as needed. In the descriptions that follow, the data type of

  the value returned is shown with each function name. The types of argu-

  ments are also given with the statement format.



  |  COMMAND  |     ABBREVIATION     |     SCREEN     |   FUNCTION TYPE   |


  |           |                      |                |                   |

  |    ABS    |     A [SHIFT+B]      |                |     NUMERIC       |

  |           |                      |                |                   |

  |    AND    |     A [SHIFT+N]      |                |                   |

  |           |                      |                |                   |

  |    ASC    |     A [SHIFT+S]      |                |     NUMERIC       |

  |           |                      |                |                   |

  |    ATN    |     A [SHIFT+T]      |                |     NUMERIC       |

  |           |                      |                |                   |

  |    CHR$   |     C [SHIFT+H]      |                |     STRING        |

  |           |                      |                |                   |

  |    CLOSE  |     CL [SHIFT+O]     |                |                   |

  |           |                      |                |                   |

  |    CLR    |     C [SHIFT+L]      |                |                   |

  |           |                      |                |                   |

  |    CMD    |     C [SHIFT+M]      |                |                   |

  |           |                      |                |                   |

  |    CONT   |     C [SHIFT+O]      |                |                   |

  |           |                      |                |                   |

  |    COS    |        none          |      COS       |     NUMERIC       |

  |           |                      |                |                   |

  |    DATA   |     D [SHIFT+A]      |                |                   |

  |           |                      |                |                   |

  |    DEF    |     D [SHIFT+E]      |                |                   |

  |           |                      |                |                   |

  |    DIM    |     D [SHIFT+I]      |                |                   |

  |           |                      |                |                   |

  |    END    |     E [SHIFT+N]      |                |                   |

  |           |                      |                |                   |

  |    EXP    |     E [SHIFT+X]      |                |     NUMERIC       |

  |           |                      |                |                   |

  |    FN     |        none          |       FN       |                   |

  |           |                      |                |                   |

  |    FOR    |     F [SHIFT+O]      |                |                   |

  |           |                      |                |                   |

  |    FRE    |     F [SHIFT+R]      |                |     NUMERIC       |

  |           |                      |                |                   |

  |    GET#   |        none          |      GET#      |                   |

  |           |                      |                |                   |

  |    GOSUB  |     GO [SHIFT+S]     |                |                   |

  |           |                      |                |                   |

  |    GOTO   |     G [SHIFT+O]      |                |                   |

  |           |                      |                |                   |

  |    IF     |        none          |       IF       |                   |

  |           |                      |                |                   |

  |    INPUT  |        none          |     INPUT      |                   |

  |           |                      |                |                   |

  |    INPUT# |     I [SHIFT+N]      |                |                   |

  |           |                      |                |                   |

  |    INT    |        none          |      INT       |     NUMERIC       |

  |           |                      |                |                   |

  |    LEFT$  |     LE [SHIFT+F]     |                |     STRING        |

  |           |                      |                |                   |

  |    LEN    |        none          |      LEN       |     NUMERIC       |

  |           |                      |                |                   |

  |    LET    |     L [SHIFT+E]      |                |                   |

  |           |                      |                |                   |

  |    LIST   |     L [SHIFT+I]      |                |                   |

  |           |                      |                |                   |

  |    LOAD   |     L [SHIFT+O]      |                |                   |

  |           |                      |                |                   |

  |    LOG    |        none          |      LOG       |     NUMERIC       |

  |           |                      |                |                   |

  |    MID$   |     M [SHIFT+I]      |                |     STRING        |

  |           |                      |                |                   |

  |    NEW    |        none          |      NEW       |                   |

  |           |                      |                |                   |

  |    NEXT   |     N [SHIFT+E]      |                |                   |

  |           |                      |                |                   |

  |    NOT    |     N [SHIFT+O]      |                |                   |

  |           |                      |                |                   |

  |    ON     |        none          |       ON       |                   |

  |           |                      |                |                   |

  |    OPEN   |     O [SHIFT+P]      |                |                   |

  |           |                      |                |                   |

  |    OR     |        none          |       OR       |                   |

  |           |                      |                |                   |

  |    PEEK   |     P [SHIFT+E]      |                |     NUMERIC       |

  |           |                      |                |                   |

  |    POKE   |     P [SHIFT+O]      |                |                   |

  |           |                      |                |                   |

  |    POS    |        none          |      POS       |     NUMERIC       |

  |           |                      |                |                   |

  |    PRINT  |          ?           |       ?        |                   |

  |           |                      |                |                   |

  |    PRINT# |     P [SHIFT+R]      |                |                   |

  |           |                      |                |                   |

  |    READ   |     R [SHIFT+E]      |                |                   |

  |           |                      |                |                   |

  |    REM    |        none          |      REM       |                   |

  |           |                      |                |                   |

  |    RESTORE|     RE [SHIFT+S]     |                |                   |

  |           |                      |                |                   |

  |    RETURN |     RE [SHIFT+T]     |                |                   |

  |           |                      |                |                   |

  |    RIGHT$ |     R [SHIFT+I]      |                |     STRING        |

  |           |                      |                |                   |

  |    RND    |     R [SHIFT+N]      |                |     NUMERIC       |

  |           |                      |                |                   |

  |    RUN    |     R [SHIFT+U]      |                |                   |

  |           |                      |                |                   |

  |    SAVE   |     S [SHIFT+A]      |                |                   |

  |           |                      |                |                   |

  |    SGN    |     S [SHIFT+G]      |                |     NUMERIC       |

  |           |                      |                |                   |

  |    SIN    |     S [SHIFT+I]      |                |     NUMERIC       |

  |           |                      |                |                   |

  |    SPC(   |     S [SHIFT+P]      |                |     SPECIAL       |

  |           |                      |                |                   |

  |    SQR    |     S [SHIFT+Q]      |                |     NUMERIC       |

  |           |                      |                |                   |

  |    STATUS |          ST          |       ST       |     NUMERIC       |

  |           |                      |                |                   |

  |    STEP   |     ST [SHIFT+E]     |                |                   |

  |           |                      |                |                   |

  |    STOP   |     S [SHIFT+T]      |                |                   |

  |           |                      |                |                   |

  |    STR$   |     ST [SHIFT+R]     |                |     STRING        |

  |           |                      |                |                   |

  |    SYS    |     S [SHIFT+Y]      |                |                   |

  |           |                      |                |                   |

  |    TAB(   |     T [SHIFT+A]      |                |     SPECIAL       |

  |           |                      |                |                   |

  |    TAN    |        none          |      TAN       |     NUMERIC       |

  |           |                      |                |                   |

  |    THEN   |     T [SHIFT+H]      |                |                   |

  |           |                      |                |                   |

  |    TIME   |         TI           |       TI       |     NUMERIC       |

  |           |                      |                |                   |

  |    TIME$  |         TI$          |      TI$       |     STRING        |

  |           |                      |                |                   |

  |    TO     |        none          |       TO       |                   |

  |           |                      |                |                   |

  |    USR    |     U [SHIFT+S]      |                |     NUMERIC       |

  |           |                      |                |                   |

  |    VAL    |     V [SHIFT+A]      |                |     NUMERIC       |

  |           |                      |                |                   |

  |    VERIFY |     V [SHIFT+E]      |                |                   |

  |           |                      |                |                   |

  |    WAIT   |     W [SHIFT+A]      |                |                   |


  |                      BASIC 4.0 DISK COMMANDS                          |


  |  COMMAND  |     ABBREVIATION     |     SCREEN     |   FUNCTION TYPE   |


  |           |                      |                |                   |

  |    APPEND |     A [SHIFT+P]      |                |    DISK/FILE      |

  |           |                      |                |                   |

  |    BACKUP |     B [SHIFT+A]      |                |    DUAL DISK      |

  |           |                      |                |                   |

  |    COLLECT|     CO [SHIFT+L]     |                |    DISK           |

  |           |                      |                |                   |

  |    CONCAT |     CON [SHIFT+C]    |                |    DISK/FILE      |

  |           |                      |                |                   |

  |    COPY   |     CO [SHIFT+P]     |                |    DISK/DUAL DISK |

  |           |                      |                |                   |

  |    DCLOSE |     D [SHIFT+C]      |                |    DISK/FILE      |

  |           |                      |                |                   |

  |  DIRECTORY|     DI [SHIFT+R]     |                |    DISK/FILE      |

  |           |                      |                |                   |

  |    DLOAD  |     D [SHIFT+L]      |                |    DISK/FILE      |

  |           |                      |                |                   |

  |    DOPEN  |     D [SHIFT+O]      |                |    DISK/FILE      |

  |           |                      |                |                   |

  |    DS     |     DS               |                |    NUMERIC        |

  |           |                      |                |                   |

  |    DS$    |     DS$              |                |    STRING         |

  |           |                      |                |                   |

  |    DSAVE  |     D [SHIFT+S]      |                |    DISK/FILE      |

  |           |                      |                |                   |

  |    HEADER |     H [SHIFT+E]      |                |    DISK           |

  |           |                      |                |                   |

  |    RECORD |     RE [SHIFT+C]     |                |    DISK/FILE      |

  |           |                      |                |                   |

  |    RENAME |     RE [SHIFT+N]     |                |    DISK/FILE      |

  |           |                      |                |                   |

  |    SCRATCH|     S [SHIFT+C]      |                |    DISK/FILE      |




  TYPE: Function-Numeric

  FORMAT: ABS([expression])

    Action: Returns the absolute value of the number, which is its value

  without any signs. The absolute value of a negative number is that

  number multiplied by -1.

  EXAMPLES of ABS Function:

    10 X = ABS (Y)

    10 PRINT ABS (X*J)



  TYPE: Operator

  FORMAT: [expression] AND [expression]

    Action: AND is used in Boolean operations to test bits. it is also used

  in operations to check the truth of both operands.

    In Boolean algebra, the result of an AND operation is 1 only if both

  numbers being ANDed are 1. The result is 0 if either or both is 0


  EXAMPLES of 1-Bit AND operation:

            0         1         0         1

        AND 0     AND 0     AND 1     AND 1

       ------     -----     -----     -----

            0         0         0         1

    The Commodore PET performs the AND operation on numbers in the range

  from -32768 to +32767. Any fractional values are not used, and numbers

  beyond the range will cause an ?ILLEGAL QUANTITY error message. When

  converted to binary format, the range allowed yields 16 bits for each

  number. Corresponding bits are ANDed together, forming a 16-bit result

  in the same range.

  EXAMPLES of 16-Bit AND Operation:


                                    AND 194



                       AND 0000000011000010


                  (BINARY) 0000000000000000


                 (DECIMAL)                0


                                  AND 28761



                       AND 0111000001011001


                  (BINARY) 0111000000000001


                 (DECIMAL)            28673


                                  AND 15359



                       AND 0011101111111111


                  (BINARY) 0011101100001111


                 (DECIMAL)            15119

    When evaluating a number for truth or falsehood, the computer assumes

  the number is true as long as its value isn't 0. When evaluating a

  comparison, it assigns a value of -I if the result is true, while false

  has a value of 0. In binary format, -1 is all 1's and 0 is all 0's.

  Therefore, when ANDing true/false evaluations, the result will be true if

  any bits in the result are true.

  EXAMPLES of Using AND with True/False Evaluations:


       AND W=3 ARE TRUE


       AND Q=7 IS TRUE


  TYPE: Function-Numeric

  FORMAT: ASC([string])

    Action: ASC will return a number from 0 to 255 which corresponds to

  the Commodore ASCII value of the first character in the string. The table

  of Commodore ASCII values is shown in (64 ref. guide) Appendix C.


    10 PRINT ASC("Z")

    20 X = ASC("ZEBRA")

    30 J = ASC(J$)

    If there are no characters in the string, an ?ILLEGAL QUANTITY error

  results. In the third example above, if J$="", the ASC function will not

  work. The GET and GET# statement read a CHR$(0) as a null string. To

  eliminate this problem, you should add a CHR$(0) to the end of the

  string as shown below.


    30 J = ASC(J$ + CHR$(0))


  TYPE: Function-Numeric

  FORMAT: ATN([number])

    Action: This mathematical function returns the arctangent of the

  number. The result is the angle (in radians) whose tangent is the number

  given. The result is always in the range -pi/2 to +pi/2.

  EXAMPLES of ATN Function:

    10 PRINT ATN(0)

    20 X = ATN(J)*180/ {pi} : REM CONVERT TO DEGREES


  TYPE: Function-String

  FORMAT: CHR$ ([number])

    Action: This function converts a Commodore ASCII code to its character

  equivalent. See Appendix C for a list of characters and their codes. The

  number must have a value between 0 and 255, or an ?ILLEGAL QUANTITY error

  message results.

  EXAMPLES of CHR$ Function:

    10 PRINT CHR$(65) : REM 65 = UPPER CASE A

    20 A$=CHR$(13) : REM 13 = RETURN KEY



  TYPE: I/O Statement

  FORMAT: CLOSE [file number]

    Action: This statement shuts off any data file or channel to a device.

  The file number is the same as when the file or device was OPENed (see

  OPEN statement and the section on INPUT/OUTPUT programming).

    When working with storage devices like cassette tape and disks, the

  CLOSE operation stores any incomplete buffers to the device. When this

  is not performed, the file will be incomplete on the tape and unreadable

  on the disk. The CLOSE operation isn't as necessary with other devices,

  but it does free up memory for other files. See your external device

  manual for more details.

  EXAMPLES of CLOSE Statement:

    10 CLOSE 1

    20 CLOSE X

    30 CLOSE 9*(1+J)


  TYPE: Statement


    Action: This statement makes available RAM memory that had been used

  but is no longer needed. Any BASIC program in memory is untouched, but

  all variables, arrays, GOSUB addresses, FOR...NEXT loops, user-defined

  functions, and files are erased from memory, and their space is mode

  available to new variables, etc.

    In the case of files to the disk and cassette tape, they are not

  properly CLOSED by the CLR statement. The information about the files is

  lost to the computer, including any incomplete buffers. The disk drive

  will still think the file is OPEN. See the CLOSE statement for more

  information on this.

  EXAMPLE of CLR Statement:

    10 X=25

    20 CLR

    30 PRINT X





  TYPE: I/O Statement

  FORMAT: [file number] [,string]

    Action: This statement switches the primary- output device from the TV

  screen to the file specified. This file could be on disk, tape, printer,

  or an I/O device like the modem. The file number must be specified in a

  prior OPEN statement. The string, when specified, is sent to the file.

  This is handy for titling printouts, etc.

    When this command is in effect, any PRINT statements and LIST commands

  will not display on the screen, but will send the text in the same

  format to the file.

    To re-direct the output back to the screen, the PRINT# command should

  send a blank line to the CMD device before CLOSEing, so it will

  stop expecting data (called "un-listening" the device).

    Any system error (like ?SYNTAX ERROR) will cause output to return to

  the screen. Devices aren't un-listened by this, so you should send a

  blank line after an error condition. (See your printer or disk manual for

  more details.)

  EXAMPLES of CMD Statement:





    30 FOR L = 1 TO 100


    50 NEXT




  TYPE: Command


    Action: This command re-starts the execution of a program which was

  halted by a STOP or END statement or the [RUN/STOP] key being pressed.

  The program will re-start at the exact place from which it left off.

    While the program is stopped, the user can inspect or change any

  variables or look at the program. When debugging or examining a program,

  STOP statements can be placed at strategic locations to allow examination

  of variables and to check the flow of the program.

    The error message CAN'T CONTINUE will result from editing the program

  (even just hitting [RETURN] with the cursor on an unchanged line), or if

  the program halted due to an error, or if you caused an error before

  typing CONT to re-start the program.

  EXAMPLE of CONT Command:

    10 PI=0:C=1

    20 PI=PI+4/C-4/(C+2)

    30 PRINT PI

    40 C=C+4:GOTO 20

    This program calculates the value of PI. RUN this program, and after

  a short while hit the [RUN/STOP] key. You will see the display:


    BREAK IN 20  | NOTE: Might be different number. |


    Type the command PRINT C to see how far the Commodore PET has gotten.

  Then use CONT to resume from where the Commodore PET left off.


  TYPE: Function

  FORMAT: COS ([number])

    Action: This mathematical function calculates the cosine of the number,

  where the number is an angle in radians.

  EXAMPLES of COS Function:

    10 PRINT COS(0)



  TYPE: Statement

  FORMAT: DATA [list of constants]

    Action: DATA statements store information within a program. The program

  uses the information by means of the READ statement, which pulls

  successive constants from the DATA statements.

    The DATA statements don't have to be executed by the program, they

  only have to be present. Therefore, they are usually placed at the end of

  the program.

    All data statements in a program are treated as a continuous list. Data

  is READ from left to right, from the lowest numbered line to the highest.

  If the READ statement encounters data that doesn't fit the type requested

  (if it needs a number and finds a string) an error message occurs.

    Any characters can be included as data, but if certain ones are used

  the data item must be enclosed by quote marks (" "). These include

  punctuation like comma (,), colon (:), blank spaces, and shifted letters,

  graphics, and cursor control characters.

  EXAMPLES of DATA Statement:

    10 DATA 1,10,5,8



    40 DATA -1.7E-9, 3.33


  TYPE: Statement

  FORMAT: DEF FN [name] ( [variable] ) = [expression]

    Action: This sets up a user-defined function that can be used later in

  the program. The function can consist of any mathematical formula. User-

  defined functions save space in programs where a long formula is used in

  several places. The formula need only be specified once, in the

  definition statement, and then it is abbreviated as a function name. It

  must be executed once, but any subsequent executions are ignored.

    The function name is the letters FN followed by any variable name. This

  can be 1 or 2 characters, the first being a letter and the second a

  letter or digit.

  EXAMPLES of DEF FN Statement:

    10 DEF FN A(X)=X+7

    20 DEF FN AA(X)=Y*Z

    30 DEF FN A9(Q) = INT(RND(1)*Q+1)

    The function is called later in the program by using the function name

  with a variable in parentheses. This function name is used like any other

  variable, and its value is automatically calculated,


    40 PRINT FN A(9)

    50 R=FN AA(9)

    60 G=G+FN A9(10)

    In line 50 above, the number 9 inside the parentheses does not affect

  the outcome of the function, because the function definition in line 20

  doesn't use the variable in the parentheses. The result is Y times Z,

  regardless of the value of X. In the other two functions, the value in

  parentheses does affect the result.


  TYPE: Statement

  FORMAT: DIM [variable] ( [subscripts] )[

          [variable] ( [subscripts] )...]

    Action: This statement defines an array or matrix of variables. This

  allows you to use the variable name with a subscript. The subscript

  points to the element being used. The lowest element number in an array

  is zero, and the highest is the number given in the DIM statement, which

  has a maximum of 32767.

    The DIM statement must be executed once and only once for each array.

  A REDIM'D ARRAY error occurs if this line is re-executed. Therefore,

  most programs perform all DIM operations at the very beginning.

    There may be any number of dimensions and 255 subscripts in an array,

  limited only by the amount of RAM memory which is available to hold the

  variables. The array may be mode up of normal numeric variables, as shown

  above, or of strings or integer numbers. If the variables are other than

  normal numeric, use the $ or % signs after the variable name to indicate

  string or integer variables,

    If an array referenced in a program was never DiMensioned, it is

  automatically dimensioned to 11 elements in each dimension used in the

  first reference.

  EXAMPLES of DIM Statement:

    10 DIM A(100)

    20 DIM Z (5,7), Y(3,4,5)

    30 DIM Y7%(Q)

    40 DIM PH$(1000)



    10 DIM S(1,5), T$(1)

    20 INPUT"TEAM NAMES"; T$(0), T$(1)

    30 FOR Q=1 TO 5: FOR T=0 TO 1


    50 INPUT S(T,Q): S(T,0)= S(T,0)+ S(T,Q)

    60 NEXT T,Q



    90 FOR Q= 1 TO 5

   100 PRINT TAB(Q*2+9) Q;

   110 NEXT: PRINT TAB(15) "TOTAL"

   120 FOR T=0 TO 1: PRINT T$(T);

   130 FOR Q= 1 TO 5

   140 PRINT TAB(Q*2+9) S(T,Q);

   150 NEXT: PRINT TAB(15) S(T,0)

   160 NEXT


    5 bytes for the array name

    2 bytes for each dimension

    2 bytes/element for integer variables

    5 bytes/element for normal numeric variables

    3 bytes/element for string variables

    1 byte for each character in each string element


  TYPE: Statement


    Action: This finishes a program's execution and displays the READY

  message, returning control to the person operating the computer. There

  may be any number of END statements within a program. While it is not

  necessary to include any END statements at all, it is recommended that

  a program does conclude with one, rather than just running out of lines.

    The END statement is similar to the STOP statement. The only difference

  is that STOP causes the computer to display the message BREAK IN LINE XX

  and END just displays READY. Both statements allow the computer to resume

  execution by typing the CONT command.

  EXAMPLES of END Statement:


    20 INPUT A$

    30 IF A$ = "NO" THEN END

    40 REM REST OF PROGRAM . . .

    999 END


  TYPE: Function-Numeric

  FORMAT: EXP ( [number] )

    Action: This mathematical function calculates the constant e

  (2.71828183) raised to the power of the number given. A value greater

  than 88.0296919 causes an ?OVERFLOW error to occur.

  EXAMPLES of EXP Function:

    10 PRINT EXP (1)

    20 X = Y*EXP (Z*Q)


  TYPE: Function-Numeric

  FORMAT: FN [name] ( [number] )

    Action: This function references the previously DEFined formula spec-

  ified by name. The number is substituted into its place (if any) and the

  formula is calculated. The result will be a numeric value.

    This function can be used in direct mode, as long as the statement

  DEFining it has been executed.

    If an FN is executed before the DEF statement which defines it, an

  UNDEF'D FUNCTION error occurs.

  EXAMPLES of FN (User-Defined) Function:


    1100 J = FN J(7)+ FN J(9)

    9990 IF FN B7 (1+1)= 6 THEN END

  FOR ... TO ... [STEP ...

  TYPE: Statement

  FORMAT: FOR [variable] = [start] TO [limit] [ STEP [increment] ]

    Action: This is a special BASIC statement that lets you easily use a

  variable as a counter. You must specify certain parameters: the

  floating-point variable name, its starting value, the limit of the count,

  and how much to add during each cycle.

    Here is a simple BASIC program that counts from 1 to 10, PRINTing

  each number and ENDing when complete, and using no FOR statements:

    100 L = 1

    110 PRINT L

    120 L = 1 + 1

    130 IF L <= 10 THEN 110

    140 END

  Using the FOR statement, here is the same program:

    100 FOR L = 1 TO 10

    110 PRINT L

    120 NEXT L

    130 END

    As you can see, the program is shorter and easier to understand using

  the FOR statement.

    When the FOR statement is executed, several operations take place.

  The [start] value is placed in the [variable] being used in the

  counter. In the example above, a I is placed in L.

    When the NEXT statement is reached, the [increment] value is added to

  the [variable]. If a STEP was not included, the [increment] is set to

  + 1. The first time the program above hits line 120, 1 is added to L,

  so the new value of L is 2.

    Now the value in the [variable] is compared to the [limit]. If the

  [limit] has not been reached yet, the program GOes TO the line after

  the original FOR statement. In this case, the value of 2 in L is less

  than the limit of 10, so it GOes TO line 110.

    Eventually, the value of [limit] is exceeded by the [variable]. At

  that time, the loop is concluded and the program continues with the line

  following the NEXT statement. In our example, the value of L reaches

  11, which exceeds the limit of 10, and the program goes on with line


    When the value of [increment] is positive, the [variable] must

  exceed the [limit], and when it is negative it must become less than

  the [limit].


  | NOTE: A loop always executes at least once. |


  EXAMPLES of FOR...TO...STEP...Statement:

    100 FOR L = 100 TO 0 STEP -1

    100 FOR L = PI TO 6* {pi} STEP .01

    100 FOR AA = 3 TO 3


  TYPE: Function

  FORMAT: FRE ( [variable] )

  Action: This function tells you how much RAM is available for your

  program and its variables. If a program tries to use more space than is

  available, the OUT OF MEMORY error results.

    The number in parentheses can have any value, and it is not used in

  the calculation.


  | NOTE: If the result of FRE is negative, add 65536 to the FRE number   |

  | get the number of bytes available in memory.                          |


  EXAMPLES of FRE Function:

    PRINT FRE(0)

    10 X = (FRE(K)-1000)/7



  | NOTE: The following always tells you the current available RAM:       |

  | PRINT FRE(0) - (FRE(0) < 0)* 65536                                    |



  TYPE: Statement

  FORMAT: GET [variable list]

    Action: This statement reads each key typed by the user. As the user is

  typing, the characters are stored in the Commodore PET's keyboard buffer.

  Up to 10 characters are stored here, and any keys struck after the 10th

  are lost. Reading one of the characters with the GET statement makes room

  for another character.

    If the GET statement specifies numeric data, and the user types a key

  other than a number, the message ?SYNTAX ERROR appears. To be safe, read

  the keys as strings and convert them to numbers later.

    The GET statement can be used to avoid some of the limitations of the

  INPUT statement. For more on this, see the section on Using the GET

  Statement in the Programming Techniques section.

  EXAMPLES of GET Statement:


    20 GET A$, B$, C$, D$, E$: REM READS 5 KEYS

    30 GET A, A$


  TYPE: I/O Statement

  FORMAT: GET# [file number], [variable list]

    Action: This statement reads characters one-at-a-time from the device

  or file specified. It works the same as the GET statement, except that

  the data comes from a different place than the keyboard. If no character

  is received, the variable is set to an empty string (equal to "") or to 0

  for numeric variables. Characters used to separate data in files, like

  the comma (,) or [RETURN] key code (ASC code of 13), are received like

  any other character.

    When used with device #3 (TV screen), this statement will read char-

  acters one by one from the screen. Each use of GET# moves the cursor 1

  position to the right. The character at the end of the logical line is

  changed to a CHR$ (13), the [RETURN] key code.

  EXAMPLES of GET# Statement:

    5 GET#1, A$

    10 OPEN 1,3: GET#1, Z7$

    20 GET#1, A, B, C$, D$


  TYPE: Statement

  FORMAT: GOSUB [line number]

    Action: This is a specialized form of the GOTO statement, with one

  important difference: GOSUB remembers where it came from. When the

  RETURN statement (different from the [RETURN] key on the keyboard)

  is reached in the program, the program jumps back to the statement

  immediately following the original GOSUB statement.

    The major use of a subroutine (GOSUB really means GO to a SUBroutine)

  is when a small section of program is used by different sections of the

  program. By using subroutines rather than repeating the same lines over

  and over at different places in the program, you can save lots of program

  space. In this way, GOSUB is similar to DEF FN. DEF FN lets you save

  space when using a formula, while GOSUB saves space when using a several-

  line routine. Here is an inefficient program that doesn't use GOSUB:


    110 FOR L = 1 TO 500:NEXT


    130 FOR L = 1 TO 500:NEXT


    150 FOR L = 1 TO 500:NEXT


    170 FOR L = 1 TO 500:NEXT

  Here is the same program using GOSUB:


    110 GOSUB 200


    130 GOSUB 200


    150 GOSUB 200


    170 GOSUB 200

    180 END

    200 FOR L = 1 TO 500 NEXT

    210 RETURN

    Each time the program executes a GOSUB, the line number and position

  in the program line are saved in a special area called the "stack,"

  which takes up 256 bytes of your memory. This limits the amount of data

  that can be stored in the stack. Therefore, the number of subroutine

  return addresses that can be stored is limited, and care should be taken

  to make sure every GOSUB hits the corresponding RETURN, or else you'll

  run out of memory even though you have plenty of bytes free.


  TYPE: Statement

  FORMAT :GOTO [line number]

	  or GO TO [line number]

    Action: This statement allows the BASIC program to execute lines out

  of numerical order. The word GOTO followed by a number will make the

  program jump to the line with that number. GOTO NOT followed by a number

  equals GOTO 0. It must have the line number after the word GOTO.

    It is possible to create loops with GOTO that will never end. The

  simplest example of this is a line that GOes TO itself, like 10 GOTO 10.

  These loops can be stopped using the [RUN/STOP] key on the keyboard.

  EXAMPLES of GOTO Statement:

    GOTO 100

    10 GO TO 50

    20 GOTO 999


  TYPE: Statement

  FORMAT: IF [expression] THEN [line number]

	  IF [expression] GOTO [line number]

	  IF [expression] THEN [statements]

    Action: This is the statement that gives BASIC most of its "intelli-

  gence," the ability to evaluate conditions and take different actions de-

  pending on the outcome.

    The word IF is followed by an expression, which can include variables,

  strings, numbers, comparisons, and logical operators. The word THEN

  appears on the same line and is followed by either a line number or one

  or more BASIC statements. When the expression is false, everything after

  the word THEN on that line is ignored, and execution continues with the

  next line number in the program. A true result makes the program either

  branch to the line number after the word THEN or execute whatever other

  BASIC statements are found on that line.

  EXAMPLE of IF...GOTO...Statement:


    110 IF N <= 0 GOTO 200


    130 GOTO 100


    210 GOTO 100

    This program prints out the square root of any positive number. The IF

  statement here is used to validate the result of the INPUT. When the

  result of N <= 0 is true, the program skips to line 200, and when the

  result is false the next line to be executed is 120. Note that THEN GOTO

  is not needed with IF...THEN, as in line 110 where GOTO 200 actually

  means THEN GOTO 200.

  EXAMPLE OF IF...THEN...Statement:

    100 FOR L = 1 TO 100

    110 IF RND(1) < .5 THEN X=X+1: GOTO 130

    120 Y=Y+1

    130 NEXT L

    140 PRINT "HEADS=" X

    150 PRINT "TAILS= " Y

  The IF in line 110 tests a random number to see if it is less than .5.

  When the result is true, the whole series of statements following the

  word THEN are executed: first X is incremented by 1, then the program

  skips to line 130. When the result is false, the program drops to the

  next statement, line 120.


  TYPE: Statement

  FORMAT: INPUT [ "[prompt]" ; ] [variable list]

    Action: This is a statement that lets the person RUNning the program

  "feed" information into the computer. When executed, this statement

  PRINTs a question mark (?) on the screen, and positions the cursor 1

  space to the right of the question mark. Now the computer waits, cursor

  blinking, for the operator to type in the answer and press the [RETURN]


    The word INPUT may be followed by any text contained in quote marks

  (""). This text is PRINTed on the screen, followed by the question mark.

    After the text comes a semicolon (;) and the name of one or more

  variables separated by commas. This variable is where the computer

  stores the information that the operator types. The variable can be any

  legal variable name, and you can have several different variable

  names, each for a different input.

  EXAMPLES of INPUT Statement:

    100 INPUT A

    110 INPUT B, C, D

    120 INPUT "PROMPT"; E

    When this program RUNs, the question mark appears to prompt the

  operator that the Commodore PET is expecting an input for line 100. Any

  number typed in goes into A, for later use in the program. If the answer

  typed was not a number, the ?REDO FROM START message appears, which means

  that a string was received when a number was expected.

    If the operator just hits [RETURN] without typing anything, the vari-

  able's value doesn't change.

    Now the next question mark, for line 110, appears. If we type only

  one number and hit the [RETURN], Commodore PET will now display 2

  question marks (??), which means that more input is required. You can

  just type as many inputs as you need separated by commas, which prevents

  the double question mark from appearing. If you type more data than the

  INPUT statement requested, the ?EXTRA IGNORED message appears, which

  means that the extra items you typed were not put into any variables.

    Line 120 displays the word PROMPT before the question mark appears. The

  semicolon is required between the prompt and any list of variables.

    The INPUT statement can never be used outside a program. The Commodore

  PET needs space for a buffer for the INPUT variables, the same space that

  is used for commands.


  TYPE: I/O Statement

  FORMAT: INPUT# [file number] , [variable list]

    Action: This is usually the fastest and easiest way to retrieve data

  stored in a file on disk or tape. The data is in the form of whole vari-

  ables of up to 80 characters in length, as opposed to the one-at-a-time

  method of GET#. First, the file must have been OPENed, then INPUT# can

  fill the variables.

    The INPUT# command assumes a variable is finished when it reads a

  RETURN code (CHR$ (13)), a comma (,), semicolon (;), or colon (:).

  Quote marks can be used to enclose these characters when writing if

  they are needed (see PRINT# statement).

    If the variable type used is numeric, and non-numeric characters are

  received, a BAD DATA error results. INPUT# can read strings up to 80

  characters long, beyond which a STRING TOO LONG error results.

    When used with device #3 (the screen), this statement will read an

  entire logical line and move the cursor down to the next line.

  EXAMPLES of INPUT# Statement:

  10 INPUT#1,A

  20 INPUT#2,A$,B$


  TYPE: Integer Function

  FORMAT: INT ([numeric])

    Action: Returns the integer value of the expression. If the expression

  is positive, the fractional part is left off. If the expression is

  negative, any fraction causes the next lower integer to be returned.

  EXAMPLES of INT Function:

    120 PRINT INT(99.4343), INT(-12.34)

     99       -13


  TYPE: String Function

  FORMAT: LEFT$ ([string], [integer])

    Action: Returns a string comprised of the leftmost [integer] char-

  acters of the [string]. The integer argument value must be in the range

  0 to 255. If the integer is greater than the length of the string, the

  entire string will be returned. If an [integer] value of zero is used,

  then a null string (of zero length) is returned.

  EXAMPLES of LEFT$ Function:


    20 B$ = LEFT$(A$,9): PRINT B$




  TYPE: Integer Function

  Format: LEN ([string])

    Action: Returns the number of characters in the string expression.

  Non-printed characters and blanks are counted.

  EXAMPLE of LEN Function:




  TYPE: Statement

  FORMAT: [LET] [variable] = [expression]

    Action: The LET statement can be used to assign a value to a variable.

  But the word LET is optional and therefore most advanced programmers

  leave LET out because it's always understood and wastes valuable memory.

  The equal sign (=) alone is sufficient when assigning the value of an

  expression to a variable name.

  EXAMPLES of LET Statement:

    10 LET D= 12              (This is the same as D = 12)

    20 LET E$ = "ABC"

    30 F$ = "WORDS"

    40 SUM$= E$ + F$          (SUM$ would equal ABCWORDS)


  TYPE: Command

  FORMAT: LIST [[[first-line]]-[[last-line]]]

    Action: The LIST command allows you to look at lines of the BASIC

  program currently in the memory of your Commodore PET. This lets you use

  your computer's powerful screen editor, to edit programs which you've

  LISTed both quickly and easily.

    The LIST system command displays all or part of the program that is

  currently in memory on the default output device. The LIST will normally

  be directed to the screen and the CMD statement can be used to switch

  output to an external device such as a printer or a disk. The LIST com-

  mand can appear in a program, but BASIC always returns to the system

  READY message after a LIST is executed.

    When you bring the program LIST onto the screen, the "scrolling" of

  the display from the bottom of the screen to the top can be slowed by

  holding down the ConTRoL [OFF/RVS] key. LIST is aborted by typing the

  [RUN/STOP] key.

    If no line-numbers are given the entire program is listed. If only the

  first-line number is specified, and followed by a hyphen (-), that line

  and all higher-numbered lines are listed. If only the last line-number is

  specified, and it is preceded by a hyphen, then all lines from the

  beginning of the program through that line are listed. If both numbers

  are specified, the entire range, including the line-numbers LISTed, is


  EXAMPLES of LIST Command:

    LIST            (Lists the program currently in memory.)

    LIST 500        (Lists line 500 only.)

    LIST 150-       (Lists all lines from 150 to the end.)

    LIST -1000      (Lists all lines from the lowest through 1000.)

    LIST 150-1000   (Lists lines 150 through 1000, inclusive.)

    10 PRINT "THIS  IS LINE 10"

    20 LIST                             (LIST used in Program Mode)

    30 PRINT "THIS  IS LINE 30"



  TYPE: Command

  FORMAT: LOAD["[file-name]"][,[device]]

    Action: The LOAD statement reads the contents of a program file from

  tape or disk into memory. That way you can use the information LOADed

  or change the information in some way. The device number is optional,

  but when it is left out the computer will automatically default to 1, the

  cassette unit. The disk unit is normally device number 8. The LOAD closes

  all open files and, if it is used in direct mode, it performs a CLR

  (clear) before reading the program. If LOAD is executed from within a

  program, the program is RUN. This means that you can use LOAD to "chain"

  several programs together. None of the variables are cleared during a

  chain operation.

    If you are using file-name pattern matching, the first file which

  matches the pattern is loaded. The asterisk in quotes by itself ("*")

  causes the first file-name in the disk directory to be loaded. if the

  filename used does not exist or if it is not a program file, the BASIC

  error message ?FILE NOT FOUND occurs.

    When LOADing programs from tape, the [file-name] can be left out, and

  the next program file on the tape will be read.  When the program is found,

  the "FOUND" message is displayed and the file will be loaded. Programs will

  LOAD starting at the memory location from which it was saved.

  EXAMPLES of LOAD Command:

    LOAD or LOAD"",1             (Reads the next program on tape unit

                                 #1, and LOADs it into the same

                                 part of memory that it came from.

                                 Use ,2 to access second cassette port.)

    LOAD A$                      (Uses the name in A$ to search)

    LOAD"*",8                    (LOADs first program or last program

                                 accessed from disk)

    LOAD"STAR TREK"              (LOAD a file from tape)





    LOAD"0:FUN",8                (LOAD a file name "FUN" from disk drive 0

    SEARCHING FOR FUN            on device 8 - 1 is second drive on dual

    LOADING                      disk drives)


               Note: Unlike the VIC, 64, C16 Plus/4 and C128/D LOAD can only

                     LOAD a file to the specific memory location from

                     which the program was saved on the disk or tape,

                     there is no relocating load routines  built into the PET)


  TYPE: Floating-Point Function

  FORMAT: LOG([numeric])

    Action: Returns the natural logarithm (log to the base of e) of the

  argument. If the value of the argument is zero or negative the BASIC

  error message ?ILLEGAL QUANTITY will occur.

  EXAMPLES of LOG Function:

    25 PRINT LOG(45/7)


    10 NUM=LOG(ARG)/LOG(10)  (Calculates the LOG of ARG to the base 10)


  TYPE: String Function

  FORMAT: MID$([string],[numeric-1][,[numeric-2]])

    Action: The MID$ function returns a sub-string which is taken from

  within a larger [string] argument. The starting position of the sub-

  string is defined by the [numeric-1] argument and the length of the

  sub-string by the [numeric-2] argument. Both of the numeric arguments

  can have values ranging from 0 to 255.

    If the [numeric-1] value is greater than the length of the [string],

  or if the [numeric-2] value is zero, then MID$ gives a null string value.

  If the [numeric-2] argument is left out, then the computer will assume

  that a length of the rest of the string is to be used. And if the source

  string has fewer characters than [numeric-2], from the starting position

  to the end of the string argument, then the whole rest of the string is


  EXAMPLE of MID$ Function:

    10 A$="GOOD"


    30 PRINT A$ + MID$(B$,8,8)



  TYPE: Command


    Action: The NEW command is used to delete the program currently in

  memory and clear all variables. Before typing in a new program, NEW

  should be used in direct mode to clear memory. NEW can also be used in

  a program, but you should be aware of the fact that it will erase

  everything that has gone before and is still in the computer's memory.

  This can be particularly troublesome when you're trying to debug your



  | BE CAREFUL: Not clearing out an old program before typing a new one   |

  | can result in a confusing mix of the two programs.                    |


  EXAMPLES of NEW Command:

    NEW             (Clears the program and all variables)

    10 NEW          (Performs a NEW operation and STOPs the program.)


  TYPE: Statement

  FORMAT: NEXT[[counter]][,[counter]]...

    Action: The NEXT statement is used with FOR to establish the end of a

  FOR...NEXT loop. The NEXT need not be physically the last statement

  in the loop, but it is always the last statement executed in a loop. The

  [counter] is the loop index's variable name used with FOR to start the

  loop. A single NEXT can stop several nested loops when it is followed by

  each FOR's [counter] variable name(s). To do this each name must appear

  in the order of inner-most nested loop first, to outer-most nested loop

  last. When using a single NEXT to increment and stop several variable

  names, each variable name must be separated by commas. Loops can be

  nested to 9 levels. If the counter variable(s) are omitted, the counter

  associated with the FOR of the current level (of the nested loops) is


    When the NEXT is reached, the counter value is incremented by 1 or by

  an optional STEP value. It is then tested against an end-value to see if

  it's time to stop the loop. A loop will be stopped when a NEXT is found

  which has its counter value greater than the end-value.

  EXAMPLES of NEXT Statement:

    10 FOR J=1 TO 5: FOR K=10 TO 20: FOR N=5 TO -5 STEP - 1

    20 NEXT N,K,J            (Stopping Nested Loops)

    10 FOR L=1 TO 100

    20 FOR M=1 TO 10

    30 NEXT M

    400 NEXT L               (Note how the loops do NOT cross each other)

    10 FOR A=1 TO 10

    20 FOR B=1 TO 20

    30 NEXT

    40 NEXT                  (Notice that no variable names are needed)


  TYPE: Logical Operator

  FORMAT: NOT [expression]

    Action: The NOT logical operator "complements" the value of each bit

  in its single operand, producing an integer "twos-complement" result. In

  other words, the NOT is really saying, "if it isn't. When working with a

  floating-point number, the operands are converted to integers and any

  fractions are lost. The NOT operator can also be used in a comparison to

  reverse the true/false value which was the result of a relationship test

  and therefore it will reverse the meaning of the comparison. In the first

  example below, if the "twos-complement" of "AA" is equal to "BB" and if

  "BB" is NOT equal to "CC" then the expression is true.

  EXAMPLES of NOT Operator:

    10 IF NOT AA = BB AND NOT(BB = CC) THEN...

    NN% = NOT 96: PRINT NN%



  | NOTE: TO find the value of NOT use the expression X=(-(X+1)). (The    |

  | two's complement of any integer is the bit complement plus one.)      |



  TYPE: Statement

  FORMAT: ON [variable] GOTO / GOSUB [line-number][,[line-number]]...

    Action: The ON statement is used to GOTO one of several given line-

  numbers, depending upon the value of a variable. The value of the

  variables can range from zero through the number of lines given. if the

  value is a non-integer, the fractional portion is left off. For example,

  if the variable value is 3, ON will GOTO the third line-number in the


    If the value of the variable is negative, the BASIC error message

  ?ILLEGAL QUANTITY occurs. If the number is zero, or greater than the

  number of items in the list, the program just "ignores" the statement and

  continues with the statement following the ON statement.

    ON is really an underused variant of the IF...THEN...statement. Instead

  of using a whole lot of IF statements each of which sends the program to

  1 specific line, 1 ON statement can replace a list of IF statements. When

  you look at the first example you should notice that the 1 ON statement

  replaces 4 IF...THEN... statements.

    EXAMPLES of ON Statement:

  ON -(A=7)-2*(A=3)-3*(A<3)-4*(A>7)GOTO 400,900,1000,100

  ON X GOTO 100,130,180,220

  ON X+3 GOSUB 9000,20,9000

  100 ON NUM GOTO 150,300,320,390

  500 ON SUM/2 + 1 GOSUB 50,80,20


  TYPE: I/O Statement

  FORMAT: OPEN [file-num],[[device]][,[address]]

           [,"[File-name] [,[type]] [,[mode]]"]

    Action: This statement OPENs a channel for input and/or output to a

  peripheral device. However, you may NOT need all those parts for every

  OPEN statement. Some OPEN statements require only 2 codes:



    The [file-num] is the logical file number, which relates the OPEN,

  CLOSE, CMD, GET#, INPUT#, and PRINT# statements to each other and

  associates them with the file-name and the piece of equipment being used.

  The logical file number can range from 1 to 255 and you can assign it any

  number you want in that range.


  | NOTE: File numbers over 128 were really designed for other uses so    |

  | it's good practice to use only numbers below 127 for file numbers.    |


    Each peripheral device (printer, disk drive, cassette) in the system

  has its own number which it answers to. The [device] number is used with

  OPEN to specify on which device the data file exists. Peripherals like

  cassette decks, disk drives or printers also answer to several secondary

  addresses. Think of these as codes which tell each device what operation

  to perform. The device logical file number is used with every GET#,

  INPUT#, and PRINT#.

    If the [device] number is left out the computer will automatically

  assume that you want your information to be sent to and received from

  the Datassette(TM), which is device number 1. The file-name can also be

  left out, but later on in your program, you can NOT call the file by name

  if you have not already given it one. When you are storing files on cas-

  sette tape, the computer will assume that the secondary [address] is

  zero (0) if you omit the secondary address (a READ operation).

    A secondary address value of one (1) OPENs cassette tape files for

  writing. A secondary address value of two (2) causes an end-of-tape

  marker to be written when the file is later closed. The end-of-tape

  marker prevents accidentally reading past the end of data which results

  in the BASIC error message ?DEVICE NOT PRESENT.

    For disk files, the secondary addresses 2 thru 14 are available for

  data-files, but other numbers have special meanings in DOS commands.

  You must use a secondary address when using your disk drive(s). (See

  your disk drive manual for DOS command details.)

    The [file-name] is a string of 1-16 characters and is optional for

  cassette or printer files. If the file [type] is left out the type of

  file will automatically default to the Program file unless the [mode] is


  Sequential files are OPENed for reading [mode]=R unless you specify that

  files should be OPENed for writing [mode] =W is specified. A file [type]

  can be used to OPEN an existing Relative file. Use REL for [type] with

  Relative files. Relative and Sequential files are for disk only.

    If you try to access a file before it is OPENed the BASIC error message

  ?FILE NOT OPEN will occur. If you try to OPEN a file for reading which

  does not exist the BASIC error message ?FILE NOT FOUND will occur. If

  a file is OPENed to disk for writing and the file-name already exists,

  the DOS error message FILE EXISTS occurs. There is no check of this type

  available for tape files, so be sure that the tape is properly positioned

  or you might accidentally write over some data that had previously been

  SAVED. If a file is OPENed that is already OPEN, the BASIC error message

  FILE OPEN occurs. (See Printer Manual for further details.)

  EXAMPLES of OPEN Statements:

    10 OPEN 2,8,4,"DISK-OUTPUT,SEQ,W"  (Opens sequential file on disk)

    10 OPEN 1,1,2,"TAPE-WRITE"         (Write End-of-File on Close)

    10 OPEN 50,0                       (Keyboard input)

    10 OPEN 12,3                       (Screen output)

    10 OPEN 130,4                      (Printer output)

    10 OPEN 1,1,0,"NAME"               (Read from cassette #1)

    10 OPEN 1,2,1,"NAME"               (Write to cassette #2)

    10 OPEN 1,4,0,"STRING"             (Send upper case/graphics to

                                        the printer)

    10 OPEN 1,4,7,"STRING"             (Send upper/lower case to


    10 OPEN 1,5,7,"STRING"             (Send upper/lower case to

                                        printer with device # 5)

    10 OPEN 1,8,15,"COMMAND"           (Send a command to disk)


  TYPE: Logical Operator

  FORMAT: [operand] OR [operand]

  Action: Just as the relational operators can be used to make decisions

  regarding program flow, logical operators can connect two or more re-

  lations and return a true or false value which can then be used in a

  decision. When used in calculations, the logical OR gives you a bit

  result of I if the corresponding bit of either or both operands is 1.

  This will produce an integer as a result depending on the values of the

  operands. When used in comparisons the logical OR operator is also used

  to link two expressions into a single compound expression. If either of

  the expressions are true, the combined expression value is true (-1). In

  the first example below if AA is equal to BB OR if XX is 20, the

  expression is true.

    Logical operators work by converting their operands to 16-bit, signed,

  two's complement integers in the range of -32768 to +32767. If the

  operands are not in the range an error message results. Each bit of the

  result is determined by the corresponding bits in the two operands.

  EXAMPLES of OR Operator:

    100 IF (AA=BB) OR (XX=20) THEN...

    230 KK%=64 OR 32: PRINT KK%         (You typed this with a bit

                                         value of 1000000 for 64

                                         and 100000 for 32)

    96                                  (The computer responded with

                                         bit value 1100000.



  TYPE: Integer Function

  FORMAT: PEEK([numeric])

    Action: Returns an integer in the range of 0 to 255, which is read

  from a memory location. The [numeric] expression is a memory location

  which must be in the range of 0 to 65535. If it isn't then the BASIC

  error message ?ILLEGAL QUANTITY occurs.

  EXAMPLES of PEEK Function:

    10 PRINT PEEK(53280) AND 15   (Returns value of screen border color)

    5 A%=PEEK(45)+PEEK(46)*256    (Returns address of BASIC variable table)


  TYPE: Statement

  FORMAT: POKE [location],[value]

  Action: The POKE statement is used to write a one-byte (8-bits) binary

  value into a given memory location or input/output register. The

  [location] is an arithmetic expression which must equal a value in the

  range of 0 to 65535. The [value] is an expression which can be reduced to

  an integer value of 0 to 255. If either value is out of its respective

  range, the BASIC error message ?ILLEGAL QUANTITY occurs.

    The POKE statement and PEEK statement (which is a built-in function

  that looks at a memory location) are useful for data storage, controlling

  graphics displays or sound generation, loading assembly language sub-

  routines, and passing arguments and results to and from assembly language

  subroutines. In addition, Operating System parameters can be examined

  using PEEK statements or changed and manipulated using POKE statements.

  A complete memory map of useful locations is given in Appendix G.

  EXAMPLES of POKE Statement:

    POKE 32768, 1         (Puts an "A" at position 1 on the screen)

    10 POKE RED,32

    20 POKE 36879,8

    2050 POKE A,B


  TYPE: Integer Function

  FORMAT: POS ([dummy])

    Action: Tells you the current cursor position which, of course, is in

  the range of 0 (leftmost character) though position 79 on an 80-character

  logical screen line. If the Commodore PET has a 40-column screen, any

  position from 40 through 79 will refer to the second screen line. The

  dummy argument is ignored.

  EXAMPLE of POS Function:

    1000 IF POS(0)>38 THEN PRINT CHR$(13)


  TYPE: Statement

  FORMAT: PRINT [[variable]][[,/;][variable]]...

    Action: The PRINT statement is normally used to write data items to

  the screen. However, the CMD statement may be used to re-direct that

  output to any other device in the system. The [variable(s)] in the

  output-list are expressions of any type. If no output-list is present, a

  blank line is printed. The position of each printed item is determined by

  the punctuation used to separate items in the output-list.

    The punctuation characters that you can use are blanks, commas, or

  semicolons. The 80-character logical screen line is divided into 8 print

  zones of 10 spaces each. In the list of expressions, a comma causes the

  next value to be printed at the beginning of the next zone. A semicolon

  causes the next value to be printed immediately following the previous

  value. However, there are two exceptions to this rule:

    1) Numeric items are followed by an added space.

    2) Positive numbers have a space preceding them.

    When you use blanks or no punctuation between string constants or

  variable names it has the same effect as a semicolon. However, blanks

  between a string and a numeric item or between two numeric items will

  stop output without printing the second item.

    If a comma or a semicolon is at the end of the output-list, the next

  PRINT statement begins printing on the same line, and spaced accord-

  ingly. If no punctuation finishes the list, a carriage-return and a line-

  feed are printed at the end of the data. The next PRINT statement will

  begin on the next line. If your output is directed to the screen and the

  data printed is longer than 40 columns, the output is continued on the

  next screen line.

    There is no statement in BASIC with more variety than the PRINT

  statement. There are so many symbols, functions, and parameters

  associated with this statement that it might almost be considered as a

  language of its own within BASIC; a language specially designed for

  writing on the screen.

  EXAMPLES of PRINT Statement:


     5 X = 5

    10 PRINT -5*X,X-5,X+5,X^5

    -25     0     10     3125


     5 X=9


    20 PRINT X "CUBED IS" X^3

    9 SQUARED IS 81 AND 9 CUBED IS 729



    100 PRINT AA$BB$;CC$ DD$,EE$


  Quote Mode

    Once the quote mark (") is typed, the cursor controls stop

  operating and start displaying reversed characters which actually stand

  for the cursor control you are hitting. This allows you to program these

  cursor controls, because once the text inside the quotes is PRINTed they

  perform their functions. The [INST/DEL] key is the only cursor control

  not affected by "quote mode."

  1. Cursor Movement

    The cursor controls which can be "programmed" in quote mode are:

          KEY                             APPEARS AS

        [CLR/HOME]                        reversed s

        [SHIFT+CLR/HOME]               reversed heart/S

        [CRSR UP/DOWN]                    reversed Q

        [SHIFT+CRSR UP/DOWN]         reversed circle or Q

        [CRSR LEFT/RIGHT]                 reversed ]

        [SHIFT+CRSR LEFT/RIGHT]      reversed verticle line

    If you wanted the word HELLO to PRINT diagonally from the upper left

  corner of the screen, you would type:


  2. Reverse Characters

    Holding down the [OFF/RVS] will cause [R] to appear

  inside the quotes. This will make all characters start printing in

  reverse video (like a negative of a picture). To end the reverse printing

  hit [SHIFT+OFF/RVS], or else PRINT a [RETURN] (CHR$(13)). (Just ending the

  PRINT statement without a semicolon or comma will take care of this.)

  4. Insert Mode

    The spaces created by using the [INST/DEL] key have some of the same

  characteristics as quote mode. The cursor controls and color controls

  show up as reversed characters. The only difference is in the [INST] and

  [DEL], which performs its normal function even in quote mode, now

  creates the [T]. And [INST], which created a special character in quote

  mode, inserts spaces normally.

    Because of this, it is possible to create a PRINT statement containing

  DELetes, which cannot be PRINTed in quote mode. Here is an example

  of how this is done:


    When the above line is RUN, the word displayed will be HELP, because

  the last two letters are deleted and the P is put in their place.


  | WARNING: The DELetes will work when LISTing as well as PRINTing, so   |

  | editing a line with these characters will be difficult.               |


    The "insert mode" condition is ended when the [RETURN] (or

  [SHIFT+RETURN]) key is hit, or when as many characters have been typed as

  spaces were inserted.

  5. Other Special Characters

    There are some other characters that can be PRINTed for special

  functions, although they are not easily available from the keyboard. In

  order to get these into quotes, you must leave empty spaces for them in

  the line, hit [RETURN] or [SHIFT+RETURN], and go back to the spaces with

  the cursor controls. Now you must hit [RVS ON], to start typing reversed

  characters, and type the keys shown below:

          Function                    Type               Appears As

    [SHIFT+RETURN]                    [SHIFT+M]   reversed M or graphic slash

    switch to lower case*             [N]                 reversed n

    switch to upper case*             [SHIFT+N] reversed N or graph. backslash

    The [SHIFT+RETURN] will work in the LISTing as well as PRINTing, so

  editing will be almost impossible if this character is used. The LISTing

  will also look very strange.

  * The case switching characters will only work in 4000/8000 series PETs.


  TYPE: I/O Statement

  FORMAT: PRINT#[file-number][[variable]][[,/;][variable]]...

    Actions: The PRINT# statement is used to write data items to a logical

  file. It must use the same number used to OPEN the file. Output goes to

  the device-number used in the OPEN statement. The [variable] expressions

  in the output-list can be of any type. The punctuation characters between

  items are the same as with the PRINT statement and they can be used in

  the same ways. The effects of punctuation are different in two

  significant respects.

    When PRINT# is used with tape files, the comma, instead of spacing

  by print zones, has the same effect as a semicolon. Therefore, whether

  blanks, commas, semicolons or no punctuation characters are used between

  data items, the effect on spacing is the same. The data items are written

  as a continuous stream of characters. Numeric items are followed by a

  space and, if positive, are preceded by a space.

    If no punctuation finishes the list, a carriage-return and a line-feed

  are written at the end of the data. If a comma or semicolon terminates

  the output-list, the carriage-return and line-feed are suppressed. Re-

  gardless of the punctuation, the next PRINT# statement begins output in

  the next available character position. The line-feed will act as a stop

  when using the INPUT# statement, leaving an empty variable when the next

  INPUT# is executed. The line-feed can be suppressed or compensated for as

  shown in the examples below.

    The easiest way to write more than one variable to a file on tape or

  disk is to set a string variable to CHR$(13), and use that string in be-

  tween all the other variables when writing the file.

  EXAMPLES of PRINT# Statement:


    10 OPEN 1,1,1,"TAPE FILE"

    20 R$=CHR$(13)                      (By Changing the CHR$(13) to

    30 PRINT#1,1;R$;2;R$;3;R$;4;R$;5     CHR$(44) you put a "," between

    40 PRINT#1,6                         each variable. CHR$(59) would

    50 PRINT# 1,7                        put a ";" between each variable.)


    10 CO$=CHR$(44):CR$=CHR$(13)

    20 PRINT#1,"AAA"CO$"BBB",           AAA,BBB     CCCDDDEEE

       "CCC";"DDD";"EEE"CR$             (carriage return)

       "FFF"CR$;                        FFF(carriage return)

    30 INPUT#1,A$,BCDE$,F$


     5 CR$=CHR$(13)

    10 PRINT#2,"AAA";CR$;"BBB"          (10 blanks) AAA

    20 PRINT#2,"CCC";                   BBB

                                        (10 blanks)CCC

    30 INPUT#2,A$,B$,DUMMY$,C$


  TYPE: Statement

  FORMAT: READ [variable][,[variable]]...

    Action: The READ statement is used to fill variable names from con-

  stants in DATA statements. The data actually read must agree with the

  variable types specified or the BASIC error message ?SYNTAX ERROR will

  result.(*) Variables in the DATA input-list must be separated by commas.

    A single READ statement can access one or more DATA statements,

  which will be accessed in order (see DATA), or several READ statements

  can access the same DATA statement. If more READ statements are executed

  than the number of elements in DATA statements(s) in the program, the

  BASIC error message ?OUT OF DATA is printed. If the number of variables

  specified is fewer than the number of elements in the DATA statement(s),

  subsequent READ statements will continue reading at the next data

  element. (See RESTORE.)


  | *NOTE: The ?SYNTAX ERROR will appear with the line number from the    |

  | DATA statement, NOT the READ statement.                               |


  EXAMPLES of READ Statement:

    110 READ A,B,C$

    120 DATA 1,2,HELLO

    100 FOR X=1 TO 10: READ A(X):NEXT

    200 DATA 3.08, 5.19, 3.12, 3.98, 4.24

    210 DATA 5.08, 5.55, 4.00, 3.16, 3.37

    (Fills array items (line 1) in order of constants shown (line 5))




  TYPE: Statement

  FORMAT: REM [[remark]]

    Action:The REM statement makes your programs more easily understood

  when LISTed. It's a reminder to yourself to tell you what you had in

  mind when you were writing each section of the program. For instance,

  you might want to remember what a variable is used for, or some other

  useful information. The REMark can be any text, word, or character

  including the colon (:) or BASIC keywords.

    The REM statement and anything following it on the same line-number

  are ignored by BASIC, but REMarks are printed exactly as entered when

  the program is listed. A REM statement can be referred to by a GOTO or

  GOSUB statement, and the execution of the program will continue with

  the next higher program line having executable statements.

  EXAMPLES of REM Statement:



    30 SUM=SUM + VEL(X): NEXT

    40 AVG=SUM/20


  TYPE: Statement


    Action: BASIC maintains an internal pointer to the next DATA constant

  to be READ. This pointer can be reset to the first DATA constant in a

  program using the RESTORE statement. The RESTORE statement can be

  used anywhere in the program to begin re-READing DATA.

  EXAMPLES of RESTORE Statement:

    100 FOR X=1 TO 10: READ A(X): NEXT

    200 RESTORE

    300 FOR Y=1 TO 10: READ B(Y): NEXT

    4000 DATA 3.08, 5.19, 3.12, 3.98, 4.24

    4100 DATA 5.08, 5.55, 4.00, 3.16, 3.37

    (Fills the two arrays with identical data)

    10 DATA 1,2,3,4

    20 DATA 5,6,7,8

    30 FOR L= 1 TO 8

    40 READ A: PRINT A

    50 NEXT

    60 RESTORE

    70 FOR L= 1 TO 8

    80 READ A: PRINT A

    90 NEXT


  TYPE: Statement


    Action: The RETURN statement is used to exit from a subroutine called

  for by a GOSUB statement. RETURN restarts the rest of your program at

  the next executable statement following the GOSUB. If you are nesting

  subroutines, each GOSUB must be paired with at least one RETURN

  statement. A subroutine can contain any number of RETURN statements,

  but the first one encountered will exit the subroutine.

  EXAMPLE of RETURN Statement:


    20 GOSUB 1000


    40 GOSUB 1000


    60 END



  TYPE: String Function

  FORMAT: RIGHT$ ([string],[numeric])

    Action: The RIGHT$ function returns a sub-string taken from the right-

  most end of the [string] argument. The length of the sub-string is

  defined by the [numeric] argument which can be any integer in the range

  of 0 to 255. If the value of the numeric expression is zero, then a null

  string ("") is returned. If the value you give in the [numeric] argument

  is greater than the length of the [string] then the entire string is


  EXAMPLE of RIGHT$ Function:


    20 PRINT RIGHT$(MSG$,9)




  TYPE: Floating-Point Function

  FORMAT: RND ([numeric])

    Action: RND creates a floating-point random from 0.0 to 1.0. The

  computer generates a sequence of random numbers by performing cal-

  culations on a starting number, which in computer jargon is called a

  seed. The RND function is seeded on system power-up. The [numeric]

  argument is a dummy, except for its sign (positive, zero, or negative).

    If the [numeric] argument is positive, the same "pseudorandom"

  sequence of numbers is returned, starting from a given seed value. Dif-

  ferent number sequences will result from different seeds, but any se-

  quence is repeatable by starting from the same seed number. Having a

  known sequence of "random" numbers is useful in testing programs.

    If you choose a [numeric] argument of zero, then RND generates a

  number directly from a free-running hardware clock (the system "jiffy

  clock"). Negative arguments cause the RND function to be re-seeded

  with each function call.

  EXAMPLES of RND Function:

    220 PRINT INT(RND(0)*50)               (Return random integers 0-49)

    100 X=INT(RND(1)*6)+INT(RND(1)*6)+2    (Simulates 2 dice)

    100 X=INT(RND(1)*1000)+1               (Random integers from 1-1000)

    100 X=INT(RND(1)*150)+100              (Random numbers from 100-249)

    100 X=RND(1)*(U-L)+L                   (Random numbers between

                                            upper (U) and lower (L) limits)


  TYPE: Command

  FORMAT: RUN [[line-number]]

    Action: The system command RUN is used to start the program currently

  in memory. The RUN command causes an implied CLR operation to be

  performed before starting the program. You can avoid the CLeaRing

  operation by using CONT or GOTO to restart a program instead of RUN. If

  a [line-number] is specified, your program will start on that line.

  Otherwise, the RUN command starts at first line of the program. The RUN

  command can also be used within a program. If the [line-number] you

  specify doesn't exist, the BASIC error message UNDEF'D STATEMENT occurs.

    A RUNning program stops and BASIC returns to direct mode when an END or

  STOP statement is reached, when the last line of the program is finished,

  or when a BASIC error occurs during execution.

  EXAMPLES of RUN Command:

    RUN           (Starts at first line of program)

    RUN 500       (Starts at line-number 500)

    RUN X         (Starts at line X, or UNDEF'D STATEMENT ERROR

                   if there is no line X)


  TYPE: Command

  FORMAT: SAVE ["[file-name]"][,[device-number]]

    Action: The SAVE command is used to store the program that is cur-

  rently in memory onto a tape or diskette file. The program being SAVED

  is only affected by the command while the SAVE is happening. The program

  remains in the current computer memory even after the SAVE operation is

  completed until you put something else there by using another command.

  The file type will be "prg" (program). If the [device-number] is left

  out, then the PET will automatically assume that you want the program

  saved on cassette, device number 1. If the [device-number] is an [8],

  then the program is written onto disk. The SAVE statement can be used

  be used in your programs and execution will continue with the next

  statement after the SAVE is completed.

    Programs on tape are automatically stored twice, so that your Com-

  modore PET can check for errors when LOADing the program back in. When

  saving programs to tape, the [file-name] and secondary [address] are

  optional. But following a SAVE with a program name in quotes ("") or

  by a string variable (---$) helps your Commodore PET find each program

  more easily. If the file-name is left out it can NOT be LOADed by name

  later on.

    A secondary address of 2 will cause an end-of-tape marker

  to follow the program.

  EXAMPLES of SAVE Command.

    SAVE               (Write to tape without a name)

    SAVE"ALPHA",1      (Store on tape as file-name "alpha" on cassette #1)

    SAVE"ALPHA",1,2    (Store "alpha" with end-of-tape mark on Cassette #1)

    SAVE"FUN.DISK",8   (SAVES on disk (device 8 is the disk))

    SAVE A$            (Store on tape #1 with the name A$)

    10 SAVE"HI"        (SAVEs program and then move to next program line)

    SAVE"ME",1,3       (Stores to tape #1 and puts an end-of-tope marker on)


  TYPE: Integer Function

  FORMAT: SGN ([numeric])

    Action: SGN gives you an integer value depending upon the sign of the

  [numeric] argument. If the argument is positive the result is 1, if zero

  the result is also 0, if negative the result is -1.

  EXAMPLE of SGN Function:

    90 ON SGN(DV)+2 GOTO 100, 200, 300

    (jump to 100 if DV=negative, 200 if DV=0, 300 if DV=positive)


  TYPE: Floating-Point Function

  FORMAT: SIN ([numeric])

    Action: SIN gives you the sine of the [numeric] argument, in radians.

  The value of COS(X) is equal to SIN(x+3.14159265/2).

  EXAMPLE of SIN Function:

    235 AA=SIN(1.5):PRINT AA



  TYPE: String Function

  FORMAT: SPC ([numeric])

    Action: The SPC function is used to control the formatting of data, as

  either an output to the screen or into a logical file. The number of

  SPaCes given by the [numeric] argument are printed, starting at the first

  available position. For screen or tape files the value of the argument

  is in the range of 0 to 255 and for disk files up to 254. For printer

  files, an automatic carriage-return and line-feed will be performed by

  the printer if a SPaCe is printed in the last character position of a

  line. No SPaCes are printed on the following line.

  EXAMPLE of SPC Function:

    10 PRINT"RIGHT "; "HERE &";

    20 PRINT SPC(5)"OVER" SPC(14)"THERE"


    RIGHT HERE &     OVER              THERE


  TYPE: Floating-Point Function

  FORMAT: SQR ([numeric])

    Action: SQR gives you the value of the SQuare Root of the [numeric]

  argument. The value of the argument must not be negative, or the BASIC

  error message ?ILLEGAL QUANTITY will happen.

  EXAMPLE of SQR Function:

    FOR J = 2 TO 5: PRINT J*S, SQR(J*5): NEXT

    10   3.16227766

    15   3.87298335

    20   4.47213595

    25   5



  TYPE: Integer Function


    Action: Returns a completion STATUS for the last input/output operation

  which was performed on an open file. The STATUS can be read from any

  peripheral device. The STATUS (or simply ST) keyword is a system defined

  variable-name into which the KERNAL puts the STATUS of I/O operations.

  A table of STATUS code values for tape, printer, disk and RS-232 file

  operations is shown below:


  |  ST Bit | ST Numeric |    Cassette   |  IEEE-488  |    Tape Verify    |

  | Position|    Value   |      Read     |  Bus R/W   |      + Load       |


  |    0    |      1     |               |  time out  |                   |

  |         |            |               |  write     |                   |


  |    1    |      2     |               |  time out  |                   |

  |         |            |               |    read    |                   |


  |    2    |      4     |  short block  |            |    short block    |


  |    3    |      8     |   long block  |            |    long block     |


  |    4    |     16     | unrecoverable |            |   any mismatch    |

  |         |            |   read error  |            |                   |


  |    5    |     32     |    checksum   |            |     checksum      |

  |         |            |     error     |            |       error       |


  |    6    |     64     |  end of file  |     EOI    |                   |


  |    7    |   -128     |  end of tape  | device not |    end of tape    |

  |         |            |               |   present  |                   |


  EXAMPLES of STATUS Function:

    10 OPEN 1,4:OPEN 2,8,4,"MASTER FILE,SEQ,W"


    30 INPUT#2,A$,B,C



    60 PRINT#1,A$,B;C

    70 GOTO 20

    80 CLOSE1:CLOSE2

    90 GOSUB 100:END


    110 RETURN


  TYPE: Statement

  FORMAT: [STEP [expression]]

    Action: The optional STEP keyword follows the [end-value] expression in

  a FOR statement. It defines an increment value for the loop counter

  variable. Any value can be used as the STEP increment. Of course, a STEP

  value of zero will loop forever. If the STEP keyword is left out, the

  increment value will be + 1. When the NEXT statement in a FOR loop is

  reached, the STEP increment happens. Then the counter is tested against

  the end-value to see if the loop is finished. (See FOR statement for more



  | NOTE: The STEP value can NOT be changed once it's in the loop.        |


  EXAMPLES of STEP Statement:

    25 FOR XX=2 TO 20 STEP 2             (Loop repeats 10 times)

    35 FOR ZZ=0 TO -20 STEP -2           (Loop repeats 11 times)


  TYPE: Statement


    Action: The STOP statement is used to halt execution of the current

  program and return to direct mode. Typing the [RUN/STOP] key on the

  keyboard has the same effect as a STOP statement. The BASIC error message

  ?BREAK IN LINE nnnnn is displayed on the screen, followed by READY. The

  "nnnnn" is the line-number where the STOP occurs. Any open files remain

  open and all variables are preserved and can be examined. The program can

  be restarted by using CONT or GOTO statements.

  EXAMPLES of STOP Statement:

    10 INPUT#1,AA,BB,CC


    30 STOP

                    (If the variable AA is -1 and BB is equal to CC then:)


  BREAK IN LINE 30        (For any other data values)


  TYPE: String Function

  FORMAT: STR$ ([numeric])

    Action: STR$ gives you the STRing representation of the numeric value

  of the argument. When the STR$ value is converted to each variable

  represented in the [numeric] argument, any number shown is followed by

  a space and, if it's positive, it is also preceded by a space.

  EXAMPLE of STR$ Function:

    100 FLT = 1.5E4: ALPHA$ = STR$(FLT)


    15000     15000


  TYPE: Statement

  FORMAT: SYS [memory-location]

    Action: This is the most common way to mix a BASIC program with a

  machine language program. The machine language program begins at the

  location given in the SYS statement. The system command SYS is used in

  either direct or program mode to transfer control of the microprocessor

  to an existing machine language program in memory. The memory-location

  given is by numeric expression and can be anywhere in memory, RAM or ROM.

    When you're using the SYS statement you must end that section of

  machine language code with an RTS (ReTurn from Subroutine) instruction

  so that when the machine language program is finished, the BASIC

  execution will resume with the  statement following the SYS command.

  EXAMPLES of SYS Statement:

    SYS 64738                      (Jump to System Cold Start in 64 ROM)

    10 POKE 4400,96:SYS 4400       (Goes to machine code location 4400

                                    and returns immediately)


  TYPE: String Function

  FORMAT: TAB ([numeric])

    Action: The TAB function moves the cursor to a relative SPC move

  position on the screen given by the [numeric] argument, starting with

  the left-most position of the current line. The value of the argument can

  range from 0 to 255. The TAB function should only be used with the PRINT

  statement, since it has no effect if used with PRINT# to a logical


  EXAMPLE of TAB Function:


    110 INPUT#1, NAM$, AMT$

    120 PRINT NAM$ TAB(25) AMT$

    NAME                         AMOUNT

    G.T. JONES                   25.


  TYPE: Floating-Point Function

  FORMAT: TAN ([numeric])

    Action: Returns the tangent of the value of the [numeric] expression

  in radians. If the TAN function overflows, the BASIC error message

  ?DIVISION BY ZERO is displayed.

  EXAMPLE of TAN Function:

    10 XX=.785398163: YY=TAN(XX):PRINT YY



  TYPE: Numeric Function


    Action: The TI function reads the interval Timer. This type of "clock"

  is called a "jiffy clock." The "jiffy clock" value is set at zero

  (initialized) when you power-up the system. This 1/60 second interval

  timer is turned off during tape I/O.

  EXAMPLE of TI Function:



  TYPE: String Function


    Action: The TI$ timer looks and works like a real clock as long as your

  system is powered-on. The hardware interval timer (or jiffy clock) is

  read and used to update the value of TI$, which will give you a TIme

  $tring of six characters in hours, minutes and seconds. The TI$ timer can

  also be assigned an arbitrary starting point similar to the way you set

  your wristwatch. The value of TI$ is not accurate after tape I/O.

  EXAMPLE of TI$ Function:

    1 TI$ = "000000": FOR J=1 TO 10000: NEXT: PRINT TI$



  TYPE: Floating-Point Function

  FORMAT: USR ([numeric])

    Action: The USR function jumps to a User callable machine language

  SubRoutine which has its starting address pointed to by the contents of

  memory locations 1 and 2. The starting address is established before

  calling the USR function by using POKE statements to set up locations

  1-2. Unless POKE statements are used, locations 1-2 will give

  you an ?ILLEGAL QUANTITY error message.

    The value of the [numeric] argument is stored in the floating-point

  accumulator starting at location 97, for access by the Assembler code,

  and the result of the USR function is the value which ends up there when

  the subroutine returns to BASIC.

  EXAMPLES of USR Function:

    10 B=T*SIN(Y)

    20 C=USR(B/2)

    30 D=USR(B/3)


  TYPE: Numeric Function

  FORMAT: VAL ([string])

    Action: Returns a numeric VALue representing the data in the [string]

  argument. If the first non-blank character of the string is not a plus

  sign (+), minus sign (-), or a digit the VALue returned is zero. String

  conversion is finished when the end of the string or any non-digit

  character is found (except decimal point or exponential e).

  EXAMPLE of VAL Function:

    10 INPUT#1, NAM$, ZIP$

    20 IF VAL(ZIP$) < 19400 OR VAL(ZIP$) > 96699



  TYPE: Command

  FORMAT: VERIFY ["[file-name]"][,[device]]

  Action: The VERIFY command is used, in direct or program mode, to compare

  the contents of a BASIC program file on tape or disk with the program

  currently in memory. VERIFY is normally used right after a SAVE, to make

  sure that the program was stored correctly on tape or disk.

    If the [device] number is left out, the program is assumed to be on

  the Datassette(TM) which is device number 1. For tape files, if the

  [file-name] is left out, the next program found on the tape will be com-

  pared. For disk files (device number 8), the file-name must be present.

  If any differences in program text are found, the BASIC error message

  ?VERIFY ERROR is displayed.

    A program name can be given either in quotes or as a string variable.

  VERIFY is also used to position a tape just past the last program, so

  that a new program can be added to the tape without accidentally writing

  over another program.


    VERIFY                      (Checks 1st program on tape #1)






    9000 SAVE "ME",8:

    9010 VERIFY "ME",8          (Looks at device 8 for the program)


  TYPE: Statement

  FORMAT: WAIT [location],[mask-1][,[mask-2]]

    Action: The WAIT statement causes program execution to be suspended

  until a given memory address recognizes a specified bit pattern. In other

  words WAIT can be used to halt the program until some external event has

  occurred. This is done by monitoring the status of bits in the input/

  output registers, The data items used with WAIT can be any numeric

  expressions, but they will be converted to integer values. For most

  programmers, this statement should never be used. It causes the program

  to halt until a specific memory location's bits change in a specific way.

  This is used for certain I/O operations and almost nothing else.

    The WAIT statement takes the value in the memory location and performs

  a logical AND operation with the value in mask-1. If there is a mask-2 in

  the statement, the result of the first operation is exclusive-ORed with

  mask-2. In other words mask-1 "filters out" any bits that you don't want

  to test. Where the bit is 0 in mask-1, the corresponding bit in the

  result will always be 0. The mask-2 value flips any bits, so that you

  can test for an off condition as well as an on condition, Any bits being

  tested for a 0 should have a I in the corresponding position in mask-2.

    If corresponding bits of the [mask-1[ and [mask-2] operands differ, the

  exclusive-OR operation gives a bit result of 1. If corresponding bits get

  the same result the bit is 0. It is possible to enter an infinite pause

    The first example below WAITs until a key is pressed on the

  tape unit to continue with the program. The second example will WAIT

  until a sprite collides with the screen background.

  EXAMPLES of WAIT Statement:

    WAIT 1,32,32

    WAIT 6502,100             (try this if you have an upgrade ROM PET!)

    WAIT 36868,144,16         (144 & 16 are masks. 144=10010000 in binary

                               and 16=10000 in binary. The WAIT statement

                               will halt the program until the 128 bit is

                               on or until the 16 bit is off)



  TYPE: I/O Statement

  FORMAT: APPEND [device],"[file-name]"

  Open file named [file-name] on disk drive device [device]

  for data to be appended on the end.

  EXAMPLES of APPEND Statement:

    APPEND 8,"0:NAMES"   (append data to file NAMES in drive 0 of device 8)


  TYPE: Command

  FORMAT: BACKUP D[drive #] TO D[drive #]

  Sends a disk duplicate command to a dual disk drive unit (note:

  will NOT work on two single drives!) to copy disk in one drive

  (0 or 1) to the other drive (0 ot 1) Only works on error free disks

  of formats compatible with the drive used. (command assumes device 8)

  EXAMPLES of BACKUP Statement:

    BACKUP D0 TO D1  (copies contents of disk in drive 0 to blank disk

                      in drive 1)


  TYPE: Command

  FORMAT: COLLECT D[drive #]

  Sends a disk collect (DOS Validate) command to a disk drive unit which

  verifys the directory with the disk block allocation and properly closes

  any unclosed files.(command assumes device 8)

  EXAMPLES of BACKUP Statement:

    COLLECT D0  (Disk collect/validate) in drive 0, device 8.

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