Computer Start-Up

Computers have become essential to our every day lives. We use them for email, to pay bills, shop,  education purposes, research, investigations, gaming, and work. Their contributions make our lives manageable, efficient, and extremely effective. We rely on them to get things done; sometimes on the fly. But what happens when this tool ceases to behave properly, such as not able to access the Internet or open email?  Let’s examine Windows 7 start up or a/k/a the boot process.

Common Startup Phase for Windows 7:

1.) Power On Self Test ( POST)

2.) Initial boot phase.

3.) Windows Boot Manager phase.

4.) Windows Boot Loader phase

5.) Kernel Loading phase.

6.) Logon phase.

The following will illustrate a normal startup process:

After the power button is pressed begins several system checking processes starting with the  Computer Processing Unit (CPU).

Central Processing Unit

Central Processing Unit

The processor gives instructions to the Basic Input / Output System (BIOS) or EFI. These are firmware which are chips that have instructions that cannot be easily changed. This processor dependent code starts the computer no matter what operating system is installed.

Power On Self Test

The first set of instructions is the Power On Self Test (POST) and these are the system diagnostic function it performs.

1.) Initiates hardware checks which verifies the devices that are connected to the computer, such as the keyboard, printer, scanner, monitor, etc. Any device that is installed on the computer.

2.) It verifies the hard drive is present and in working order.

3.) Retrieves the system’s configurations setting from the non-volatile memory (stores information when the computer is shut-down) which includes the device boot order on the motherboard.

Directly after the POST is completed components, such as the add-on video adapter have their own firmware so they perform their own diagnostic tests.

System Beeps alert to Success or Failure

If the POST discovers a hardware failure the monitor will display the nature of the problem and the system will sound off a beep(s) which signifies the issue. For example, 1 beep indicates a Ready Access Memory (RAM) issue – 6 beep indicates a keyboard failure, and so on. Each set of beeps signifies a specific component has failed.

Operating System and More Initiated

The computer then locates the Windows Boot Manager which locates the operating system (OS) installed on the hard drive, such as XP, Vista, Windows 7, Windows 8.

The non-volatile memory settings are accessed to determine the boot order, floppy disks (if present) hard disk which is attached to Advanced Technology Attachment (ATA), Serial ATA,  and Small Computer System Interface (SCSI) controllers.

Boot Disk

The usual start up device with the bootable files is the hard drive, but other devices besides the hard drive can be configured to boot the computer, such as Network adapter, Compact Disc (CD) / Digital Versatile Disc (DVD), and removable disks. You can manually configure the system to boot from either one of these. If the computer doesn’t locate bootable files on the Compact Disc Read-Only Memory (CD_ROM) it will search the boot order.

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If by chance the start up process fails during the POST it could be an issue with the BIOS, the hard disk, or a system file. If this occurs then the monitor will display an error message “Non-system disk error – Replace and press any key when ready.” This error is an indication that none of the available disks have bootable files; in other words a boot disk. Has this ever happened to you?

Troubleshoot:

-This could be a critical issue or very simple one to resolve it’s good to know which it is.  Read my article “Why Should I Care” for an example.

– Check the computer ports to ensure all removable disks including USBs are removed.

– Verify the boot order. 1. Floppy – 2. Optical Drive (DVD, CD-ROM), 3. Hard Drive 4. Network Adapter

– If the boot order is intact then it’s most likely the Master Boot Record (MBR) which may be corrupt.

Boot Manager Process

The MBR is located on the hard drive’s first 512bytes. It contains the boot code instructions which is the table describing the characteristics of the active partition and extended partitions. The BIOS reads the contents of the MBR into memory and then transfers control to it.

It reads the content of the file system and finds the 16bit stub program called the Boot Manager in the root directory. It then switches into the 64bit Protected Mode and loads the 64bit Windows Boot Manager. The active partition starts Windows Boot Loader. You’ll never see the Boot Loader because it actually doesn’t have a user interface. What this does is allow the user to press any key to display the boot menu or press F8 for Advanced Boot Options. If a key is not press then Windows Boot Manager starts the Boot Loader and Window 7 splash screen displays. Continued


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Author: Wanda

4 thoughts on “Computer Start-Up

  1. Arielle

    Incredible! This blog looks just like my old one!
    It’s on a completely different topic but it has pretty much the same layout and design. Superb choice of colors! Not the mention the information is very interesting plus informative for those who have no idea what’s happening behind the computer scenes.

    Reply
    1. Wanda Post author

      This is the reason why I’ve written this topic, Arielle. It’s to inform and you might say educate users on how their computer works.

      Thank you,

      Wanda

      Reply
  2. Melissa

    Great blog here! It’s a little confusing at first as I read it a second time and believe it or not I see clarity. Whoa!

    Reply
    1. Wanda Post author

      That’s the idea, Melissa. You know many times I have to re-read literature to get a clear perspective? You are not alone.

      Cheers!

      Wanda

      Reply

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