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(.exe) DOS EXE File Structure

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Offset Size Description
00 word "MZ" - Link file .EXE signature
02 word length of image mod 512
04 word size of file in 512 byte pages
06 word number of relocation items following header
08 word size of header in 16 byte paragraphs, used to locate the beginning of the load module
0A word min # of paragraphs needed to run program
0C word max # of paragraphs the program would like
0E word offset in load module of stack segment (in paragraphs)
10 word initial SP value to be loaded
12 word negative checksum of pgm used while by EXEC loads pgm
14 word program entry point, (initial IP value)
16 word offset in load module of the code segment (in paragraphs)
18 word offset in .EXE file of first relocation item
1A word overlay number (0 for root program)

Registers at load time of the EXE file are as follows:

AX contains number of characters in command tail, or 0
BX:CX 32 bit value indicating the load module memory size DX zero
SS:SP set to stack segment if defined else, SS = CS and SP=FFFFh or top of memory.
DS set to segment address of EXE header
ES set to segment address of EXE header
CS:IP far address of program entry point, (label on "END" statement of program)