Monday, December 8, 2014



The primary function of the computer system unit is to hold all the other components together and protect the sensitive electronic parts from the outside elements. A typical computer case is also large enough to allow for upgrades, such as adding a second hard drive or a higher-quality video card. It is relatively easy to open up a computer system unit to replace parts and install upgrades. In contrast, it is quite difficult to open up a laptop computer, which is not designed with replacements and upgrades in mind. In most computer system units, the front side contains the elements a user needs frequently, such as the power button, an optical disk drive, an audio outlet for a pair of headphones, and a number of USB connections. The back side contains all other connections - for power, monitor, keyboard, mouse, Internet connection, and any other peripheral devices. There are typically more connections than the minimum necessary to allow for expansion.

Front View:


Parts and there Function

What Are the Functions of CD-ROM Drive?

CD-ROM drives are very popular for playing and installing media. CD-ROM drives are classified as 5.25-inch drives because they fit into the 5.25-inch drive bays that are used in computer cases. CD-ROM drives come in many forms, including external, internal, and more.

Data Reading:

CD-ROM drives can open documents on data CDs, such as music files, pictures, word documents and other files. However, CD-ROM drives can not write information to a CD (burn) because they are read-only drives; writing information to a CD is done with a CD-R drive.

Music Playback:

CDs can be created in two forms, an audio CD and a data CD. Data CDs can only be opened by computers and other CD players. However, audio CDs can be played by any CD player, such as in most newer car stereos or a portable CD player.

Software Installation:

CDs are widely used as installation discs. Whenever there is software included with a product that you buy in a store, or just the software itself, it is highly likely that it is stored on a CD. Before software could be downloaded off the Internet, it was exclusively distributed in CDs and floppy diskettes.

Other Function for CD-ROM/DVD-ROM/ROM Drive:

Is an optical disc storage media format, and was invented and developed by Philips, Sony,Toshiba, and Time Warner in 1995. Its main uses are video and data storage. DVDs are of the same dimensions as compact discs (CDs), but are capable of storing almost seven times as much data.

What are the functions of Floppy Drive?

Floppy disks have mostly been replaced by other forms of file storage such as CD/DVD-ROM drives and the common USB flash drive, but many computers can still store and access information using the older technology of the floppy disk drive.


According to the University of Michigan, floppy disks have changed over time. The earliest floppy disks measured eight inches in size. Soon 5.25-inch disks replaced them, and eventually 3.5-inch floppies became the standard. Although 3.5-inch floppy disks have hard cases, the flimsy magnetic media inside remains flexible.


Floppy disks store computer files in a portable package. A typical high-density 3.5-inch floppy stores 1.44 megabytes of data, according to Jonny Pham at the University of Tennessee, Knoxville. Today, newer file storage devices have replaced floppy disks as a major mode of transfer between computers, but sometimes users will find older files stored on floppy disks.


Users can load disks into a floppy disk drive; this will cause the metal tab to slide to the side and expose the delicate disk inside for the computer to read, according to Bowling Green State University. When dealing with old floppies, users should remember that each disk type corresponds to a different type of drive. Never place a smaller disk inside a larger drive.

Reset Button:

In electronics and technology, a reset button is a button that can reset a device. On video game consoles, the reset button restarts the game, losing the player's unsaved progress. On personal computers, the reset button clears the memory and reboots the machine forcibly. Reset buttons are found on circuit breakers to reset the circuit. This button can cause data corruption so this button often doesn't exist on many machines. Usually, in computers and other electronic devices, it is present as a small button, possibly recessed into the case or only accessible by a pin or similar thin object, to prevent it being pressed accidentally.

What’s the Difference between Power Button and Reset Button in the System Unit? 

In fact, the Reset button is an integral function of the power supply itself; when you first start the PC, the Power Supply holds the Reset line high, and when the voltage is stable, it releases the line, allow the computer to start the cold boot process. However, there wasn't a button or a user-accessible line for it in the first generation of PC's (the IBM 5150, Eagle, and Compaq 4.77 MHz machines.) It wasn't until the XT clones came out, with their 8 MHz processors, that this became commonplace. The 8MHz systems crashed... a lot. Also, dependig on the tasks at hand, it was common to reboot PC's several times a day, and while Control-Alt-Delete works for most situations, it doesn't fully reset the hardware like the Rest button does. It's also not the best idea in the world to power-cycle hard drives, especially back in the day when there was a chance your drive wouldn't spin up (2 of my early hard drives had this problem; you had to pull the drive out and wiggle it around its axis a little to get it to spin up.)

Back-View of System Unit 


Power supply unit (computer) - A power supply unit (PSU) converts mains AC to low-voltage regulated DC power for the internal components of a computer. Modern personal computers universally use a switched-mode power supply. Some power supplies have a manual selector for input voltage, while others automatically adapt to the supply voltage. Most modern desktop personal computer power supplies conform to the ATX specification, which includes form factor and voltage tolerances. While an ATX power supply is connected to the mains supply, it always provides a 5 V standby (5VSB) voltage so that the standby functions on the computer and certain peripherals are powered. ATX power supplies are turned on and off by a signal from the motherboard. They also provide a signal to the motherboard to indicate when the DC voltages are in spec, so that the computer is able to safely power up and boot. The most recent ATX PSU standard is version 2.31 of mid-2008.

Other Function of Power Supply or ATX Power Supply:

The most common computer power supplies are built to conform to the ATX form factor. This enables different power supplies to be interchangeable with different components inside the computer. ATX power supplies also are designed to turn on and off using a signal from the motherboard, and provide support for modernfunctions such as thestandby mode available in many computers. The most recent specification of the ATX standard PSU as of mid-2008 is version 2.31.

Computer Keyboard - In computing, a keyboard is a typewriter-style device, which uses an arrangement of buttons or keys, to act as mechanical levers or electronic switches. Following the decline of punch cards and paper tape, interaction via teleprinter-style keyboards became the main input device for computers.A keyboard typically has characters engraved or printed on the keys and each press of a key typically corresponds to a single written symbol. However, to produce some symbols requires pressing and holding several keys simultaneously or in sequence. While most keyboard keys produce letters, numbers or signs (characters), other keys or simultaneous key presses can produce actions or execute computer commands.Despite the development of alternative input devices, such as the mouse, touchscreen, pen devices, character recognition and voice recognition, the keyboard remains the most commonly used device for direct (human) input of alphanumeric data into computers.

Mouse - In computing, a mouse is a pointing device that detects two-dimensional motion relative to a surface. This motion is typically translated into the motion of a pointer on a display, which allows for fine control of a graphical user interface. Physically, a mouse consists of an object held in one's hand, with one or more buttons. Mice often also feature other elements, such as touch surfaces and "wheels", which enable additional control and dimensional input.

Video Card - A video card (also called a video adapter, display card, graphics card, graphics board, display adapter, graphics adapter or frame buffer and sometimes preceded by the word discrete or dedicated to emphasize the distinction between this implementation and integrated graphics) is an expansion card which generates a feed of output images to a display (such as a computer monitor). Within the industry, video cards are sometimes called graphics add-in-boards, abbreviated as AIBs, with the word "graphics" usually omitted.

Other Function for Video Card/VGA - A video card, video adapter, graphics accelerator card, display adapter, or graphics card is an expansion card whose function is to generate output images to a display. Many video cards offer added functions, such as accelerated rendering of 3D scenes and 2D graphics, video capture, TV tuner adapter, MPEG-2/MPEG-4 decoding, FireWire, light pen, TV output, or the ability to connect multiple monitors (multi-monitor). Other modern high performance video cards are used for more graphically demanding purposes, such as PC games.

USB - A USB flash drive is a data storage device that includes flash memory with an integrated Universal Serial Bus (USB) interface. USB flash drives are typically removable and rewritable, and physically much smaller than an optical disc. Most weigh less than 30 grams (1.1 oz).USB flash drives are often used for the same purposes for which floppy disks or CDs were used, i.e., for storage, data back-up and transfer of computer files. They are smaller, faster, have thousands of times more capacity, and are more durable and reliable because they have no moving parts. Additionally, they are immune to magnetic interference (unlike floppy disks), and are unharmed by surface scratches (unlike CDs). Until about 2005, most desktop and laptop computers were supplied with floppy disk drives in addition to USB ports, but floppy disk drives have been abandoned due to their lower capacity compared to USB flash drives.

Ethernet - A Medium Attachment Unit (MAU) is a transceiver which converts signals on an Ethernet cable to and from Attachment Unit Interface (AUI) signals. On original 10BASE5 (Thick) Ethernet, the MAU was typically clamped to the Ethernet cable. With later standards it was generally integrated into the network interface controller and eventually the entire Ethernet controller was often integrated into a single integrated circuit ("chip") to reduce cost. In most modern switched or hubbed Ethernet over twisted pair systems, neither the MAU nor the AUI interfaces exist (apart, perhaps as notional entities for the purposes of thinking about layering the interface), and the category 5 (CAT5) cable connects directly into an Ethernet socket on the host or router. For backwards compatibility with equipment which still has external AUI interfaces, MAUs are still available with 10BASE2 or 10BASET connections.

Modem - Is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. The goal is to produce a signal that can be transmitted easily and decoded to reproduce the original digital data. Modems can be used over any means of transmitting analog signals, from driven diodes to radio.

Audio - The sound card on the motherboard lets us hear from an internal speaker. We can also plug in peripheral devices such as speakers, microphones or headphones. You should think about where you will be using your computer. If you're going to end up needing to use headphones most of the time, or speakers that are included with your system, the stock sound card will work just fine for you. If you want something that jams, you may need to upgrade.

Other Function for Sound Card -  is a computer expansion card that facilitates the input and output of audio signals to and from a computer under control of computer programs.Typical uses of sound cards include providing the audio component for multimedia applications such as music composition, editing video or audio, presentation, education, and entertainment (games). Many computers have sound capabilities built in, while others require additional expansion cards to provide for audio capability.

Printer - In computing, a printer is a peripheral which makes a persistent human-readable representation of graphics or text on paper or similar physical media. The two most common printer mechanisms are black and white laser printers used for common documents, and color ink jet printers which can produce high-quality photograph-quality output.

Expansion Card/Slots for add-ins Card - The expansion card (also expansion board, adapter card or accessory card) in computing is a printed circuit board that can be inserted into an electrical connector, or expansion slot on a computer motherboard, back plane or riser card to add functionality to a computer system via the expansion bus.



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