It's most definitely not a program 'written' by a programmer, but rather a listing of some random program segment using the disassembly command of a debugger. Have you tried to find that code within the program? Let's See What We Got Hard to say anything definitive with only this (incomplete) section. A few details visible are: 01: INT 21 ; An unknown (*1) call to DOS, function code would have been set prior to this line 02: JB 0103 ; Jump to address 0103h if DOS returns NO error ...