Self-modifying code: Difference between revisions

Revision as of 00:58, 28 April 2003

Revision as of 21:12, 28 April 2003

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Self-modifying code was used in the early days of computers in order to save memory space in computers with very small main memory sizes.

Self-modifying code was used to hide copy protection instructions in 1980s MS DOS based games. The floppy disk drive access instruction 'int 0x13' would not appear in the executable program's image but it would be written into the executable's memory image after the program started executing. It is also sometimes used by programs that does not want to reveal their presence; [[computer virus|computer virii]] and some [[shellcode]]s use this technique.

example algorithm (theoretical!)