GOSUB

Call a numbered subroutine. RETURN continues after the GOSUB. Nested GOSUB is limited to 16 levels.

GOSUB line GOSUB label RETURN

line - subroutine line number label - subroutine label

Example:

GOSUB Show
END

Show:

PRINT 6 * 7
RETURN

GOSUB Helper
END

Helper:

PRINT 42
RETURN

Source: docs/help/gosub.txt inmmcore. On the computer, typeHELP GOSUB.