21h FL$BACK back one record
Input - none -
Output X = updated record number (same as FLW_CREC)
Description Used in the OPL command BACK. Sets the current file position back to the previous record.

Should not be called with FLW_CREC (current record) = 0 or 1. The first record is numbered 1.

Example
        LDAB    #10             ; go back ten records

LOOP:   LDX     FLW_CREC        ; dont go back past start
        CPX     #1
        BCC     DONE
        OS      FL$BACK    
        DECB
        BNE     LOOP    
DONE:
Errors - none -