Smart Computing Article - Booting Your PC

November 1999 • Vol.3 Issue 4 Add To My Personal Library Getting Up Close & Personal With A Computer's BIOS Turning on your computer makes it flicker, beep, and flash messages until it's ready to roll. Those of you who have wondered what your computer was actually doing during the startup process are in for a treat. We'll spend some time going through the boot process, which is the process your PC completes when starting up, and explaining a key component to your PC's startup known as the Basic Input/Output System (BIOS). The BIOS performs several vital functions before passing control over to the user. In this article, we'll explain what the BIOS is and what it does. BIOS (pronounced bye-ohs) is a set of instructions stored on a read-only memory (ROM) chip, which makes it neither pure hardware nor software. It's more accurately called , or software inscribed in hardware. The ROM chip holds 256 kilobytes (KB) of instructions, though 512KB chips are becoming common these days. The chip is usually located on the circuit board (known as a motherboard) containing the central processing unit (CPU), or brains of the machine. The CPU reads instructions from the BIOS and executes them in a fixed order. ( NOTE: Because the BIOS is the source of these commands, the convention is to discuss the processes from the point of view of the BIOS. However, at the microprocessor level, it is really the CPU performing functions through the BIOS. The BIOS controls a PC's startup process and manages its basic components, such as the keyboard, monitor, and disk drives. Unlike random-access memory (RAM), the BIOS is stored in ROM and does not blank out when a PC is switched off. The BIOS is waiting to perform its tasks when you turn on a