TOPS-20 Commands Reference Manual


Places an executable program into the current fork, combining it with whatever program (if any) is already there.


@MERGE (PROGRAM) filespec /switch


filespec is the file specification of any executable program.

Default file type - .EXE

/switch is one or more of the following:
/OVERLAY allows pages of the DDT program to be loaded over pages occupied by the existing program in memory.
/USE-SECTION:n specifies the memory section (from 0 to 37 octal) into which your program is to be merged. You can use this switch only if your program can be contained in one section.


Executable Files Only

If a program you try to merge is not in executable format, you may get an immediate error message (that is, "?UNEXPECTED END-OF-FILE TRAP...") or a delayed one (that is, "?ENTRY VECTOR LENGTH IS NOT LESS THAN 1000") after the merge. In either case, be sure that you have specified an executable program before investigating further. The MERGE command does not alter the entry vector if the file being merged is in the proper .EXE format.

Existing Pages Not Overlaid

If there is a program already in memory when you give the MERGE command, and pages of the new program overlay it, the new program is not placed into memory, and the system prints the error message, "?Illegal to overlay existing pages." To force the existing pages to be overlaid, reissue the MERGE command using the /OVERLAY switch.

Effect on Memory

The MERGE command combines the specified program with the program in the current fork. It does not affect the contents of the current fork unless you specify the /OVERLAY switch.

Related Commands

INFORMATION MEMORY-USAGE for examining the contents of memory
GET for putting a saved (executable) file into memory
SAVE for storing a copy of the program in the current fork in a file in executable format
START for starting the program in memory


  1. Merge an executable program into memory.
  2. Place an executable system program in memory, then merge a system debugging program with it. Give INFORMATION MEMORY-USAGE commands to verify that both programs are intact.
    34. pages, Entry vector loc 4715 len 3
      Section 0     R, W, E,  Private
    0        RANDOM:<NEXT-RELEASE>DUMPER.EXE 4  1   R, CW, E
    4-44     RANDOM:<NEXT-RELEASE>DUMPER.EXE.4  2-42   R, CW, E
    45. pages, Entry vector loc 4715 len 3
      Section 0     R, W, E,  Private
    0        RANDOM:<NEXT-RELEASE>DUMPER.EXE.4  1   R, CW, E
    4-44     RANDOM:<NEXT-RELEASE>DUMPER.EXE.4  2-42   R, CW, E
    764-767  RANDOM:<NEXT-RELEASE>UDDT.EXE.1  1-4   R, CW, E
    770-776  RANDOM:<NEXT-RELEASE>UDDT.EXE.1  5-13   R, E