What is the bootstrap?

The software that runs first on the computer, bringing it up from an unknown state by a series of initialization steps and installing basic I/O drivers needed to begin loading the other software that will run the computer and perform the tasks the users needs to do.

On most modern computers the bootstrap software is stored in a Flash EEPROM (this can be rewritten with updated versions if necessary to fix bugs) so that it is always available when the computer is turned on. However on early computers the bootstrap program often had to be manually entered by the operator on a bank of switches, read in from punched cards or punched tape, read from a selected magnetic tape unit, etc. This could be a very tedious process.

On most modern computers the bootstrap program loads an operating system, which then takes control of the computer and interacts with the user - loading and running other programs as he requests them. However on early computers there was no operating system and the operator had to run the bootstrap program for each and every program he wanted to run.