BIOS

About Bios

BIOS Setup Utility

BIOS stands for the Basic Input/Output System found in Windows computers and unlike operating systems, it is integrated into the computer (i.e. users do not have to install it). The BIOS is the first application to be launched when the computer starts up and follows a series of steps to check whether all the hardware is functioning properly before loading the operating system. The very first step is to conduct a power on self test (POST) immediately after the computer is turned on, whereby the BIOS checks the CPU registers, the main memory, itself etc and identifies the devices that need to be booted.

In later versions, the BIOS is able to also organise and select which devices needed to be started. After completing the POST, the BIOS is responsible for starting up (initialising) all the major hardware, such as the CPU and the RAM. The BIOS then passes control over to the operating system of the computer. Unlike operating systems, BIOS is stored on the motherboard as Read Only Memory (ROM). Later, as the hardware of computers developed further, BIOS was stored on the Electrically Erasable Programmable Read Only Memory (EEPROM), the first versions of which were used in 1978 for the Intel 2816.

The term BIOS was first used in 1975, by Gary Kildall and was used to depict the part of a computer's hardware that was initialised when the computer was turned on and the operating system was loaded.

Read Only Memory

image of Gary Kildall

A Read Only Memory (ROM) chip is defined as a non-volatile method of storage in a computer as it doe not require power all the time to retain information, unlike the RAM, where once the computer is disconnected from its power source, the data stored in the RAM is lost. However, writing data to ROM was a slower process than writing to RAM and ROM chips could only store a fraction of the amount of data that RAM chips could. Hence, the development of BIOS is heavily reliant on the development of Processors at the time. In 1974, the Intel 8080, had an Addressable Memory of 64 Kilobytes. The amount that could be stored on a ROM chip at the time was much less. But within a decade, a rapid growth in hardware development, allowed Processors to store more data in memory (by 1985, the Intel 80386 had an addressable memory of 4 Gigabytes). As a result, the capacity of the ROM chip also increased.