Disk Defragmenter is a computer program included in Microsoft Windows designed to increase access speed by rearranging files stored on a disk to occupy contiguous storage locations.It also attempts to create larger regions of free space using compaction to impede the return of fragmentation.Disk Defragmenter is also used to improve system startup times.

Hard disks are slow in computer terms. Compared to the speed of the processor and its memory, the time it takes for the arm to move and for a sector to spin into place is an eon ,so we want minimize arm movement as much as possible, and make data stored in sequential segments on the disk .

What happens is that the disk fills up. Then you erase files to reclaim space. These files that you delete are scattered all over the surface of the disk. When you load a new application or a large file onto the disk, it ends up being stored in hundreds or thousands of these scattered pockets of space. Now when the computer tries to load the scattered pieces, the disk’s arm has to move all over the surface and it takes forever.

The idea behind the disk defragmenter is to move all the files around so that every file is stored on sequential sectors on sequential rings of the disk.

Disk Defragmenter  limitations:

• It does not defragment files residing in the Recycle Bin or files that are in use.
• Only one volume can be analyzed or defragmented at a time and only one instance can run.
• Only local volumes can be defragmented, network volumes are not supported.
• Defragmenting NTFS volumes with cluster sizes larger than 4 kilobytes (KB) is not possible.
• EFS encrypted files are not defragmented.
• NTFS metadata, such as the Master File Table (MFT), or metadata that describes a directory’s contents is not defragmented.

Basic Input/Output System (BIOS) designed to be the first code run by a PC when powered on. The initial function of the BIOS is to identify, test, and initialize system devices such as the video display card, hard disk, and floppy disk and other hardware. This is to prepare the machine into a known state, so that software stored on compatible media can be loaded, executed, and given control of the PC.This process is known as booting, or booting up, which is short for bootstrapping.

The first thing the BIOS does is check the information stored in a tiny (64 bytes) amount of RAM located on a complementary metal oxide semiconductor (CMOS) chip. The CMOS Setup provides detailed information particular to your system and can be altered as your system changes. The BIOS uses this information to modify or supplement its default programming as needed.

After checking the CMOS Setup and loading the interrupt handlers, the BIOS determines whether the video card is operational.

Next, the BIOS checks to see if this is a cold boot or a reboot.

If it is a cold boot, the BIOS verifies RAM by performing a read/write test of each memory address. It checks the PS/2 ports or USB ports for a keyboard and a mouse. It looks for a peripheral component interconnect (PCI) bus and, if it finds one, checks all the PCI cards. If the BIOS finds any errors during the POST, it will notify you by a series of beeps or a text message displayed on the screen. An error at this point is almost always a hardware problem.

BIOS then displays some details about your system.

and system start begin

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