Is this why mainframes almost never get rebooted?


Flashback to the late 1980s, when PCs are beginning to arrive at the government agency where this pilot fish works -- and not just on users' desks.

"I got a call from a mainframe programmer whose PC wouldn't boot," says fish. "My first question: What were you doing just before it stopped working? Answer: 'I had to make a configuration change to my computer, so I edited COMMAND.COM.'

"This programmer edited an executable system file? Unlikely, I thought. Regardless, I picked up a set of boot floppies and trudged next door to where the mainframe programmers didn't have to mix with the unwashed masses of everybody who wasn't a mainframer."

Sure enough, the PC doesn't boot on its own, so fish inserts the appropriate boot floppy and restarts the machine without issue. The DIR C:\ command reveals two interesting files: COMMAND.COM with 4,096 bytes -- far too small -- and COMMAND.BAK with 65K bytes.

It seems the mainframe programmer intended to edit CONFIG.SYS or AUTOEXEC.BAT, but instead used the Edlin text editor to edit COMMAND.COM, saw a screen full of hex gibberish and, instead of quitting the editor, exited it.

And Edlin dutifully copied the original file to COMMAND.BAK, then wrote its memory buffer, all 4,096 bytes of it, back to the hard drive.

"I copied a fresh version of COMMAND.COM to the hard drive, deleted COMMAND.BAK and lectured the mainframe programmer as to which configuration files were editable and which were not," fish says.

"No further problems were reported."

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