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.

The clock speed that the component is rated for is at or below the speed at which the CPU has passed the manufacturer’s functionality tests when operating in worst-case conditions (for example, the highest allowed temperature and lowest allowed supply voltage)

overclocking is the process of running a computer component at a higher clock rate than it was designed for or was specified by the manufacturer.

Overclocking a computer’s processor or memory causes it to go faster than its factory rated speed. A processor rated at 2.4GHz might be overclocked to 2.5GHz or 2.6GHz, while memory rated at 200MHz might be pushed to 220MHz or higher. The extra speed results in more work being done by the processor and/or memory in a given time period, increasing the overall computing performance of the PC.

The most obvious reason to overclock a computer system is to squeeze some additional performance out of it at little or no cost. Overclocking the processor and system memory can significantly boost game performance, benchmark scores and even simple desktop tasks. Since almost every modern processor and memory module is overclockable to at least a slight degree, there are few reasons not to attempt it.

most important considerations for overclocking :

Heat :

The faster a computer goes, the more heat it produces. This is especially true when the voltage being fed to certain components is increased, a standard overclocking method. Excess heat in the processor, motherboard chipset or memory can cause crashes and system instability, and may be one of the limiting factors in determining the maximum overclock for a system so we need more cooling when overclocking

Power Supply :

Overclocking a computer system also increases the amount of power it draws, and this may lead to system instability if its old 300Watt power supply is not up to the task. If overclocking a modern Pentium 4 or Athlon 64 system, plan on upgrading the power supply to at least 400Watts

clock rate ” Clock speeds  “ is the speed at which a microprocessor executes instructions. every computer contains an electronic clock, which produces a sequence of regular electrical pulses used by the control unit to synchronize the components of the computer and regulate the fetch-execute cycle by which program instructions are processed that regulates the rate at which instructions are executed and synchronizes all the various computer components. The CPU requires a fixed number of clock ticks (or clock cycles) to execute each instruction. The faster the clock, the more instructions the CPU can execute per second.

in other word ,  clock rate is the fundamental rate in cycles per second at which a computer performs its most basic operations such as adding two numbers or transferring a value from one processor register to another. it is the frequency of the clock in any synchronous circuit.

Clock speeds are expressed in megahertz – millions of pulses a second – (MHz)  or gigahertz (GHz).