I'm new to programming and recently studying an ancient DOS assembly program written for 80186 and assembled with MASM. There are some .obj files that I want to open and take a look. I tried obj2asm.exe and IDA 5.0 (freeware version), but both programs could not deliver accurate results. As far as I know those .obj files are just lists of data indexes in format similar to below:


INDEX1 DB 000H,000H ; A
DB 021H,000H ; B
DB 06FH,020H ; C
...... ......

There are no assembly instruction in the .obj files. What should I do in order to accurately diassemble those .obj files? This DOS program is very important to my study and I'm desperate to get the correct files. Could anyone please give me some advice? Your kind assistance is very much appreciated! Thank you in advance!

1 Answer 1


This obj (or omf) file is an assembled 8086 executable that should contain executable code (no headers).

IDA Pro can disassemble it, but the free version won't.

Ghidra can handle it.

You may have to select the processor type manually and/or set the loading address (0x100).

  • I tried Ghidra and it worked like a charm. Thanks again for your kind assistance. Have a nice day!
    – skyforest
    Commented Jan 21 at 9:19
  • You're welcome. If this answered your question - please mark the answer as accepted. Thanks
    – Yotamz
    Commented Jan 21 at 13:50

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