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The boot process
When you start a computer, it has to carry out a number of tests to ensure all components of the system are functioning correctly. This process is called booting, or booting up, the computer. No matter how good the computer system, if it can't complete the boot process, it's useless.
When you turn on the computer, nothing much seems to happen for a few seconds. In fact your computer is performing a set of operations that will check that all the components are working correctly. This operation is called the Power On Self Test or POST. It is the first part of the boot process.
As the POST is doing its job, you will see and hear indications that something is happening. For example, you might see the keyboard lights flash on for a second, you might hear floppy disk drive activity, you may see activity on the monitor, or there might be printer activity. This is because all the system components are being tested, including the CPU, the RAM, and all other components.
If there are any errors or faults found during the POST, you might see error messages on the computer display and hear beeps coming from the PC’s internal speaker. The beeps are codes that can tell you what the problem is.
If no problems are encountered during the POST, then the Operating System is loaded into memory and the boot process can continue until all systems are operating correctly.
There are two ways of booting the computer, these are:
- Warm boot - also known as a 'soft boot'. It occurs when the machine is rebooted using the Ctrl + Alt + Del keys or when you need to start the computer immediately, such as when the computer freezes or when something isn’t working properly.
- Cold boot - when the computer has been switched off for a lengthy time, usually overnight.
The difference between the two is that, in a warm boot, not all parts of the system are checked for correct operation.
The boot up sequence
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