Executable Formats
Home Up Early Material Assembler Programs&Style Project 3 Executable Formats DEBUG Disks Calculating  C/H/S Project 4
2003-09-23 11:44

Executable Formats: .COM vs. .EXE

Reference: http://www.algonquincollege.com/infosystems/pincka/dat2343/lect111.htm 

.COM Format Executable .EXE Format Executable
one single 64KByte segment many segments
Program Segment Prefix is first 0100h bytes PSP has its own segment, separate from code
CS, DS, ES, SS all point to same single segment CS points to code segment
DS, ES point to separate PSP segment
SS points to stack segment
IP always set to start at 0100h IP typically starts at zero; but, can start anywhere
stack segment is fixed size (part of code segment) separate stack segment is programmer-defined size
SP starts at FFFEh (high memory of segment) SP starts at high memory of separate stack segment
must run in Real memory (first megabyte) can run anywhere (including above 1MB)
disk file is exact copy of code memory image disk file has many segments; needs to be loaded

Web Author: Ian! D. Allen idallen@idallen.ca      Updated: 2003-09-23 11:44

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