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Knowledge/A Level/H446/01 Computer systems/Systems Software/BIOS

BIOS

1.2.1 Systems Software

Practise exam questions

Systems Software — Note 6 of 8

Candidates need to understand the role of the BIOS in a computer system, and the steps that the BIOS goes through to start a computer.

What you need to know

The Basic Input Output System (BIOS) is the first program that runs when a computer is switched on. It checks the hardware and starts the process of loading the operating system from secondary storage into RAM.

What to know

  • Step 1: the processor runs the BIOS from ROM/flash.
  • Step 2: POST (Power-On Self Test) checks that essential hardware such as RAM, the processor and the keyboard is present and working.
  • Step 3: the BIOS identifies the boot device using the configured boot order.
  • Step 4: the bootstrap loader is run, which loads the operating system kernel from secondary storage into RAM and passes control to it.
  • BIOS settings (such as boot order and the system clock) are stored in a small area of memory kept powered by a battery (CMOS).
  • Most modern computers use UEFI, a more advanced replacement for BIOS with the same purpose.

Key terms

Exam tipCommon mistake

BIOS

Firmware stored in non-volatile memory (ROM or flash) that runs when the computer is switched on, tests the hardware and loads the operating system.

  • Exam tip: The BIOS must be stored in non-volatile memory because RAM is empty when the computer is switched on.

Ready to test yourself?

Practise 1.2.1 questions
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Back to Systems Software

Systems Software

Note 6 of 8

  1. 1The need for, function and purpose of operating systems
  2. 2Memory management: paging, segmentation and virtual memory
  3. 3Interrupts, Interrupt Service Routines (ISR) and their role in the FDE cycle
  4. 4Scheduling: round robin, FCFS, multi-level feedback queues, SJF and SRT
  5. 5Distributed, embedded, multi-tasking, multi-user and real time operating systems
  6. 6BIOS
  7. 7Device drivers
  8. 8Virtual machines: executing intermediate code and running one OS within another
Topic overview