Computer and Software Support

Boot process

When you turn the computer on, It completes a certain checks called P.O.S.T. which stands for Power On Self Test. Knowing when a problem occurs during the boot up, helps determine what part of the computer is having the issue. Here is an explanation of the boot process.

  1. The computer is turned on
  2. The Central Processing Unit (CPU) initializes itself
  3. CPU checks the system's ROM BIOS for its first instructions in the startup program
  4. The ROM BIOS stores the first instruction. This is the instructions for the POST stored in a memory address.
  5. POST checks the BIOS chip and then tests the CMOS RAM.
  6. System checks all hardware such as hard drives, floppies, ports to ensure it works
  7. This is the point where you can press certain keys to enter the BIOS (check with the manufacturer for the specific keys for your BIOS)
  8. This is the point where you see the initial OEM splash screen (such as DELL, IBM, SONY, Gateway etc)
  9. Then the BIOS checks the boot sequence.  For this example, I am going to assume the boot order is Floppy first, CD-ROM second and hard drive last in the boot order (The boot sequence can be changed in the BIOS that you can modify and access during step 7 above)
    1. The system checks the Floppy to see if there is a bootable disk in the drive (bootable disk means it has instructions for the system to follow) If there is a disk in the drive without the instructions the system will hang with an error message. If there is no disk in the drive, the system will skip the floppy drive in the boot process.
    2. The system will look at the CD-ROM drive for boot instructions. If there is no CD in the drive, the system will skip the CD-ROM in the boot process. If there is a CD in the drive, the system will see if it has boot instructions. If it does, it will follow the instructions on the CD. If the CD doesn't have the boot instructions, it will normally skip the CD-ROM but may hang at the CD-ROM. If this is the case you will need to remove the CD that is in the CD-ROM and reboot the computer
    3. Now the system will check the hard drive for boot instructions. If it finds the instructions it will follow them. This is the drive the system normally boots to. It is what takes you to windows.
  10. If the system doesn't find boot instructions on any device, it will give you an error message and just hang at this point.
  11. If the system boots to the hard drive, the BIOS turns the control over to Windows.
  12. This is the point where you can press F8 to bring up the Windows Startup options to go to safe mode, last known good configuration and other options. If F8 is not pressed, it will continue the boot process.
  13. Windows will take an inventory of the hardware and software on the system (this is where you see the windows splash screen)
  14. Windows opens up to the desktop where the start button is.