Booting the Computer
by Mark B. Rosenthal
Nowadays, when people hear the phrase \"boot the computer\" many think of kicking it, as you would \"kick-start\" a motorcycle engine. But that\'s not what is meant by this use of \"boot\".
With a modern computer, when you first power it on, it already has some instructions in its memory. These instructions are in a special kind of memory called read-only-memory or ROM. The computer executes these instructions to read additional instructions from its disk, and those instructions then tell it how to load the operating system.
The first computers I ever wrote code for (DEC PDP-8\'s and PDP-11\'s) had no ROM. But they did have front panels with toggle switches that allowed you to manually enter values to be stored in memory. To start the computer you had to enter a short program, usually 6 or 7 machine instructions, in binary through the toggle switches. These instructions were a tight loop which was just barely enough to read......
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