18. OCR A Level (H046-H446) SLR4 - 1.2 BIOS

Summary

This video explains the role of the Basic Input/Output System (BIOS) in a computer's startup process. It covers how BIOS conducts the Power-On Self-Test (POST) to check hardware, and how it loads the operating system through the bootstrap process. The video differentiates BIOS from the operating system and explores how BIOS settings are stored in flash memory, allowing for modifications. Viewers will learn how BIOS can be configured to boot from different devices, offering solutions in case of OS corruption. This foundational overview of BIOS provides a clear understanding of its function in starting up a computer system.

Takeaways

• 😀 The BIOS (Basic Input/Output System) is responsible for loading the operating system when the computer starts, but it is different from the operating system itself.
• 😀 The operating system controls the hardware and software of the computer after it has loaded, whereas the BIOS handles the initial startup tasks.
• 😀 When a computer powers on, the BIOS performs a Power-On Self-Test (POST) to ensure that all necessary hardware components are functioning correctly.
• 😀 The BIOS settings are stored in flash memory, allowing changes to be made and retained even after the power is turned off.
• 😀 The BIOS can be configured to change the boot order, allowing the computer to boot from external devices like a USB drive or optical disk in case of an issue with the hard drive.
• 😀 The BIOS loads the bootstrap program, which begins the process of starting the operating system by checking hardware and loading the OS kernel into memory.
• 😀 ROM (Read-Only Memory) stores the BIOS instructions, providing the necessary startup code that is read at the time of manufacturing.
• 😀 The bootstrap (bootloader) checks storage devices for the operating system and loads the necessary boot files to prepare for the OS to take over.
• 😀 The BIOS helps initialize the system and prepare the operating system by loading files like `config.sys` and `command.com` during boot-up.
• 😀 Once the BIOS completes its tasks, the operating system takes control of the computer, managing memory, processes, and user interactions.

Q & A

What is the role of the BIOS in a computer system?

The BIOS (Basic Input/Output System) is responsible for loading the operating system when the computer first turns on. It checks that all necessary hardware is connected and working, and initiates the process that leads to the operating system being loaded into memory.

How does the BIOS differ from the operating system?

The operating system controls the hardware and software of a computer and provides a user interface. The BIOS, on the other hand, is responsible for booting the computer and preparing it to load the operating system.

What is the Power-On Self-Test (POST)?

The Power-On Self-Test (POST) is a diagnostic process run by the BIOS at startup. It checks that all the required hardware components are connected and functioning correctly before the system proceeds with booting.

What is the bootstrap program, and what does it do?

The bootstrap program, also known as the bootloader, is responsible for loading the operating system kernel into memory. It also checks the hardware and prepares the system to hand over control to the operating system.

What is the relationship between ROM, BIOS, and POST?

ROM (Read-Only Memory) stores the initial startup instructions for the computer, including the BIOS. During POST, the BIOS uses these instructions to perform diagnostics and ensure the hardware is working correctly before proceeding with the boot process.

Why are BIOS settings stored in flash memory instead of ROM?

BIOS settings are stored in flash memory because this allows them to be updated or changed when needed, and the settings are retained even when the computer is powered off, unlike ROM, which is permanent.

How does the BIOS help recover a computer when the operating system or hard disk becomes corrupted?

If the operating system or hard disk becomes corrupted, the BIOS can be configured to attempt booting from alternative devices, such as an external USB drive or optical disk, allowing the user to recover the system.

What is the function of the boot file in the BIOS startup process?

The boot file, generated during the bootstrap process, contains essential information required to load the operating system. It is stored in main memory and is used to start the operating system.

What are some examples of files the operating system looks for during boot-up?

The operating system typically looks for files such as config.sys, which configures system settings, and command.com, which contains operating system utilities and BIOS-related information.

How does the operating system take control after the BIOS completes its tasks?

Once the BIOS has completed its tasks, including loading necessary files and performing hardware checks, the operating system takes control by loading additional files, managing memory, and controlling the processor. At this point, the user can interact with the system.