1.9. System Boot

• Booting the system is done by loading the kernel into main memory, and starting its execution.

• The CPU is given a reset event, and the instruction register is loaded with a predefined memory location, where execution starts.

  • The initial bootstrap program is found in the BIOS read-only memory.
  • This program can run diagnostics, initialize all components of the system, loads and starts the Operating System loader. (Called boot strapping)
  • The loader program loads and starts the operating system.
  • When the Operating system starts, it sets up needed data structures in memory, sets several registers in the CPU, and then creates and starts the first user level program. From this point, the operating system only runs in response to interrupts. See CPU Response to Interrupts.