Bootstrap loader
<operating system> (from "
bootstrap" or "to pull oneself up by one's bootstraps") A short
program that was read in from
cards or
paper tape, or
toggled in from the front panel switches, which read in a more complex
program to which it gave control.
On early computers the bootstrap loader was always very short (great efforts were expended on making it short in order to minimise the labour and chance of error involved in toggling it in), but was just smart enough to read in a slightly more complex
program (usually from a card or
paper tape reader), to which it handed control; this
program in turn was smart enough to read the
application or
operating system from a
magnetic tape drive or
disk drive.
Thus, in successive steps, the
computer "pulled itself up by its bootstraps" to a useful operating state.
Nowadays the bootstrap is usually found in
ROM or
EPROM, and reads the first stage in from a fixed location on the
disk, called the "
boot block".
When this
program gains control, it is powerful enough to load the actual
OS and hand control over to it.
See
boot.
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