GOSUB - Call a BASIC subroutine

    GOSUB line

This statement is like the GOTO statement, except that the computer remembers from where it came. When a line with a RETURN statement is encountered, the program jumps back to the statement immediately following the GOSUB. The target of a GOSUB statement is called a subroutine. A subroutine is useful if there is a section of the program that can be used.by several different parts of the program. Instead of duplicating the section over and over, it can be set up as a subroutine and called with a GOSUB statement from different parts of the program. This also make.the main part of your program much more readable. See also the RETURN statement.

Variables are shared with the main program and all subroutines. You can pass information to, and get information back from, subroutines by using variables as messengers.

GOSUB statements can be nested. That is, one subroutine can call another subroutine, and the computer automatically keeps track of all the calls. It's important not to jump into or out of subroutines, since this can confuse the computer. If too many GOSUBs are nested (usually cause by jumping out of them) an 'OUT OF MEMORY' error is reported because the computer ran out of room to keep track of all the calls.

         10 DIR           : GOSUB 100       show directory, check status
         20 GOSUB 200                       print gap
         30 LIST "PROGRAM": GOSUB 100       show listing, check status
         40 GOSUB 200                       print gap
         50  etc...
         90 END
         99:
        100 REM SUBROUTINE TO CHECK DISK STATUS
        110 IF DS THEN GOSUB 200: PRINT "DISK ERROR: ";DS$
        120 RETURN
        199:
        200 REM SUBROUTINE TO PRINT A SPACER ON THE SCREEN
        210 PRINT
        220 FORI=1TO39:PRINT"-";:NEXT
        230 PRINT
        240 RETURN

GOTO - Transfer program execution to specified line number

    GOTO  line_number
    GO TO line_number

After a GOTO statement is executed, the next line to be executed will be the one with the line number following the word GOTO. When used in direct mode, GOTO line number allows starting of execution of the program at the given line number without clearing the variables.

    10 PRINT"COMMODORE"
    20 GOTO 10