booting is the process of powering on a computer and getting into the operating system. During the boot process, the computer will perform a self-diagnostic, also known as a POST and load necessary drivers and programs that help the computer and devices communicate. As your computer is booting, you may see a screen similar to the example picture below.
- The heart of a modern computer is one or more Central Processing Units.
- A CPU gets its instructions from memory.
- The CPU reads instruction from the BIOS and searches for the hard disks, CD drives and other hardware.
- The BIOS program looks at the first sector for boot code.
- Devices that feed the initial CPU instructions are known as bootstrap media.
- The Booting is a process involving 2 stages:
- getting hardware up and running, and
- getting the OS and other software up and running
Booting a Computer
- Power up; computer runs POST
- Boot sequence governed by BIOS ROM
- BIOS parameters stored in CMOS
- BIOS ROM may be password protected
- Control passes to the MBR of the first bootable device detected
- MBR points to boot record of selected operating system
- Operating system takes control
- What is a BIOS?
- Basic input/output system
- Built into the PC:
- BIOS software stored permanently(*) on a ROM chip on the motherboard
- The first code run when a PC is powered on
- Identify system devices
(*) In modern computers BIOS chip can be rewritten, allowing BIOS software to be upgraded.
- What is a POST?
- power-on self-test — one of the first processes that a computer undergoes when booting
- POST tests the computer to ensure that it is working as it is supposed to.
- POST can detect some errors with the processor, motherboard, RAM and other memory, as well as the video card.
- Most BIOS chips use a system of beep codes to indicate the POST status to the user and each BIOS chipset uses a different code.
- The IBM PC BIOS code standard, for example, uses one short beep to indicate a successful POST and two short beeps to indicate a POST error while AMI BIOS uses these same beep codes to indicate a DRAM refresh failure or parity circuit failure, respectively.