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VGA This is circuit board that plug into the computer internally internally & connects to the monitor.  Its function is to create the correct signals graphics on the screen. Powered by DeSiaMore2

PERFORMANCE CHARACTERISTICS Available resolution. Number of colour per pixels.  Video memory the card need to maintain the image in memory.  speed in carring out a variety of different graphic functions. Powered by DeSiaMore3

LIQUID CRYSTAL DISPLAYS The screen contains a layer of liquid crystal cells. These have unusual property of hanging the polarization of light passing through them in response to an electrical signals. Powered by DeSiaMore4

CRT( crystal relay tube )‏ The electronic are produce by an electron gun & other components allow the beam to be deflected left and right & up and down. Powered by DeSiaMore5

The processes used to produce a display with liquid crystals is as follows. a fluorescent panel generates light behind the display panel the light is filtered through a polariser. Varying electrical charges are applied to selected cells as required by the image,the molecules in these liquid crystals cells change shape and force the light to twist (change polarisation)‏ the light emerging then passes through one of three colour filters. Red,Blue, or Green that are arranged close to each other. The final colour displayed on the LCD monitor depends upon the amount of twist of the light as it passed through each of the filters. Powered by DeSiaMore6

HARD-DISK Powered by DeSiaMore7

HARD-DISK Is one of secondary Storage device(non-volatile),medium and as the repository for a user's documents, files and applications. Powered by DeSiaMore8

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Hard disks are rigid platters, composed of a substrate and a magnetic medium. The substrate - the platter's base material - must be non-magnetic and capable of being machined to a smooth finish. It is made either of aluminium alloy or a mixture of glass and ceramic. To allow data storage, both sides of each platter are coated with a magnetic medium CONSTRUCTION Powered by DeSiaMore10

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FILE SYSTEM The precise manner in which data is organized on a hard disk drive is determined by the file system used. File systems are generally operating system dependent. However, since it is the most widely used PC operating system, most other operating systems' file systems are at least read-compatible with Microsoft Windows. Powered by DeSiaMore12

The FAT file system was first introduced in the days of MS-DOS way back in The purpose of the File Allocation Table is to provide the mapping between clusters - the basic unit of logical storage on a disk at the operating system level - and the physical location of data in terms of cylinders, tracks and sectors - the form of addressing used by the drive's hardware controller.FATclusterscylinderstrackssectors Powered by DeSiaMore13

The FAT contains an entry for every file stored on the volume that contains the address of the file's starting cluster. Each cluster contains a pointer to the next cluster in the file, or an end- of-file indicator at (0xFFFF), which indicates that this cluster is the end of the file. The diagram shows three files: File1.txt uses three clusters, File2.txt is a fragmented file that requires three clusters and File3.txt fits in one cluster. In each case, the file allocation table entry points to the first cluster of the file. Powered by DeSiaMore14

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The FAT contains an entry for every file stored on the volume that contains the address of the file's starting cluster. Each cluster contains a pointer to the next cluster in the file, or an end- of-file indicator at (0xFFFF), which indicates that this cluster is the end of the file. The diagram shows three files: File1.txt uses three clusters, File2.txt is a fragmented file that requires three clusters and File3.txt fits in one cluster. In each case, the file allocation table entry points to the first cluster of the file. Powered by DeSiaMore16

FAT16, FAT32 and NTFS each use different cluster sizes depending on the size of the volume, and each file system has a maximum number of clusters it can support. The smaller the cluster size, the more efficiently a disk stores information because unused space within a cluster cannot be used by other files; the more clusters supported, the larger the volumes or partitions that can be createdvolumes Powered by DeSiaMore17

The table below provides a comparison of volume and default cluster sizes for the different Windows file systems still commonly in use: Powered by DeSiaMore18

PERFORMANCE The performance of a hard disk is very important to the overall speed of the system - a slow hard disk having the potential to hinder a fast processor like no other system component - and the effective speed of a hard disk is determined by a number of factors. Powered by DeSiaMore19