User's Guide

BSR

DITTO command ---- Back Space Records

Function:

Backspaces a specified number of physical records on the specified DITTO device. The user has the option to backspace records on the input device or output device.

Parameters:

DEVTYPE
Device type. Specifies which input/output device is to be processed. Valid values are:


  = INPUT:  Input device
  = OUTPUT: Output device

NRECS(0)
Number of records. Specifies the number of physical records to be backspaced on the input or output device.

Examples:

  1. DITTO> bsr devtype=input nrecs=2

    The user has specified to backspace two physical records from the current position on the input device.

               Before:
                                               file ptr.
                                                   |
                                                   v
               ------------------------------------------------
               |        |        |        |        |        |E|
               |record 1|record 2|record 3|record 4|record 5|O|
               |        |        |        |        |        |F|
               ------------------------------------------------
      
    
    
    
                      
    
               After:
                             file ptr.
                                 |
                                 v
               -------------------------------------------------
               |        |        |        |        |         |E|
               |record 1|record 2|record 3|record 4|record 5 |O|
               |        |        |        |        |         |F|
               -------------------------------------------------
    

  2. DITTO> bsr devtype=output nrecs=4

    The user has specified to backspace four physical records from the current position on the output device.

               Before:
                                               file ptr.
                                                   |
                                                   v
               -------------------------------------------------
               |        |        |        |        |         |E|
               |record 1|record 2|record 3|record 4|record 5 |O|
               |        |        |        |        |         |F|
               -------------------------------------------------
    
    
               After:
           file ptr.
               |
               v
               -------------------------------------------------
               |        |        |        |        |         |E|
               |record 1|record 2|record 3|record 4|record 5 |O|
               |        |        |        |        |         |F|
               -------------------------------------------------
    

Description/Algorithm:

The parameters are input into the program. From the parameter DEVTYPE, it is determined which device is to be processed. The specified number of physical records are backspaced from the current position of the DITTO device.

Nonfatal Error Messages:

    None.

Fatal Error Messages:

    None.

User Note:

    None.