is a magic file
(specifically, a .COM
file). It is, essentially, DOS
Unlike *nix, DOS's commands are embedded in command.com. Want to hack dir so it replaces all instances of e with 3, so you can be a h4x0r? Tough luck. You have to modify command.com to do that, and command.com ain't open source.
On the other hand, command.com is rather efficient in that, along with a few helper files (most notably CONFIG.SYS, and AUTOEXEC.BAT), it provides a basic OS with scripting (sort of) in less than 300k of memory. Or, it used to. Nowadays, you'd better have extended memory set up right if you want to sneeze.
An excellent example of monolithic coding.
From wharfinger: not *all* dos commands are in command.com; just most. and it runs like-named batch files before built-ins, if the .bat is in %path%. Sorry, wharfinger, I removed your mandatory microsoft rant. ;)