Computer hardware refers to the physical parts or components of a computer such as monitor, keyboard, hard drive disk, mouse, printers, graphic cards, sound cards, memory, motherboard and chips, etc all of which are physical objects that you can actually touch. Hardware components provide the physical interface to a computer system. However, they cannot function without instructions to operate them. It refers to the physical components that make up a computer system.

One of the great strengths of the PC architecture is that it is extensible, allowing a great variety of components to be added, thereby permitting the PC to perform functions its designers may never have envisioned. However, most PCs include a more-or-less standard set of components, including the following:

  1. Motherboard: The motherboard is the heart of a PC. It serves as “Command Central” to coordinate the activities of the system. Its type largely determines system capabilities.
  2. Processor: The processor or CPU is the engine that drives the PC. The CPU determines how fast the system runs and what operating systems and other software can run on it.
  3. Memory: A PC uses Random Access Memory (RAM), also simply called memory, to store the programs and data with which it is currently working.
  4. Hard disk drive: The hard disk drive (HDD) is the primary storage device on any PC.
  5. Video Card: A video card, also called a graphics card, accepts video data from the computer and converts it into a form the monitor can display.
  6. Sound Card: For performing PC audio functions, you’ll need a sound card (or embedded motherboard sound card).
  7. Floppy disk drive: The floppy disk drive (FDD) was formerly used for everything from booting the PC to storing data to running programs to making backups. CD-ROM drives : CD-ROM drives began to appear on mainstream PCs in the early 1990s.
  8. Keyboard and Mouse: PCs use several types of devices to accept user input keyboards for entering text.
  9. Case and Power supply: The case is the outer shell that contains the PC and all internal peripheral devices. The power supply provides regulated power to all system components and cooling airflow to keep components from overheating.
  10. Monitor: The display you use ultimately determines the quality of the video you see. Most PCs use traditional CRT monitors, but flat-panel LCD displays are increasingly popular choice.



The processor, also called the microprocessor or CPU (for Central Processing Unit), is the brain of the PC. It performs all general computing tasks and coordinates tasks done by memory, video, disk storage, and other system components. The Central Processing Unit, which is often referred to as the “Processor” is the brain of the computer. The chip that performs the majority of calculations and instructions needed to make your computer run. Without this chip, no other function of the PC is possible. The processor is attached to the motherboard (Processor slot). The computer’s speed or clock rate is integral to its overall design. The computers clock rate is the frequency at which it can execute a set of instructions. Computer clock rates are measured in Megahertz (million of clock ticks per second).

There are two types of speeds that should be considered when evaluating the system performance:

  1. Internal clock speed: Is the speed at which the processor can obtain information within itself, like with internal cache and registers. (Pentium III 800 MHz. the 800 MHz is the internal clock speed).
  2. External clock speed: Is the speed at veins which the CPU communicates with components outside itself.



The motherboard is the heart of a PC. Some manufacturers use the terms system board, planar board, baseboard, or main board, and Intel calls it motherboards desktop boards. It provides the common link to all other components inside the PC, including the CPU, memory, disk drives, video and sound adapters, keyboard, mouse, and other peripheral components.

The motherboard is the main circuit board inside your PC. Every component at some point communicates through the motherboard, either by directly plugging into it or by communicating through one of the motherboards ports. The motherboard is one big communication highway. Its purpose inside your PC is to provide a platform for all the other components and peripherals to talk to each other. Modern motherboards come with. the following features:

  1. Processor slot: Processor slot is used for processor.
  2. Memory banks: Memory banks are used for RAM modules.
  3. AGP slots: AGP slots are used for graphics accelerators.
  4. PCI slots: PCI slots are used to provide connectivity for PCI cards such as modems and sound cards.
  5. IDE: IDE are used to connect and control IDE devices such as hard drives and CD-ROM drives.
  6. USB ports: USB ports are used to connect USB devices.

These are just some of the features that a motherboard may have as standard, some motherboards come with integrated components such as a sound card, graphics card, modem, NIC (Network Interface Card) and more.



RAM is our working memory storage. All the data, which the PC uses and works with during operation, are stored here. Data are stored on drives, typically the hard drive. However, for the CPU to work with those data, they must be read into the working memory storage, which is made up of RAM chips.

RAM (Random Access Memory) is the basic working memory of your computer system. A computer use RAM to hold volatile (Temporary) instructions and data needed for processing. Volatile simply means that it is not permanent, which means anything written to RAM will be lost if the machine loses power or if it’s turned off. Another key point about RAM is that data stored in it can be accessed much more quickly than data retrieved from the hard disk. Theoretically data retrieved from RAM is accessed 100 to 300 times faster then the same information from a hard disk, optical drive, or a floppy. .

Memory is measured in bytes, so you’ll often encounter the terms megabyte (MB) and gigabyte (GB) in describing RAM sizes (a megabyte is a million bytes; a gigabyte, a billion). RAM is something that you do not want to skimp on. You can choose a slower processor, but with RAM you want as much as you can get.



Hard disks consist of one or more magnetic disks contained in a box. They are used as storage media in the PC, where you store programs and other digital data.

The hard disk (or hard drive) is the permanent storage area of your computer. It stores information whether the computer is on or off. A hard drive is a mass storage device found in all PCs (with some exclusions) that is used to store permanent data such as the operating system, programs and user files.

The data on hard drives can be erased and/or overwritten, the hard drive is classed as a non-volatile storage device which means it doesn’t require a constant power supply in order to retain the information stored on it (unlike RAM).

Inside every hard drive are small round disklike objects made of either an aluminum/alloy or a glass/ceramic composite, these are called platters, each platter is coated with a special magnetic coating enabling them to store data magnetically. Hovering above these platters are read/write heads that transfer data to and from the platters.

Hard drives come with many different storage capacities, hard drive capacity is measured in bytes, with common capacities being stated in MB (Megabytes) and GB (Gigabytes).



Many computers come with video built into the motherboard. However, many motherboards do not have built-in video, and some that do also have AGP slots for additional or replacement of video adapters.

A computer video adapter is placed in the motherboard, where it transfers video signals through a cable to your monitor. The video adapter can either be built into the motherboard or be a separate card that is placed in either the AGP or PCI-Express Slot.

The computer graphics cards major job in a computer is to convert graphic patterns into signals for the monitor’s screen. However in recent times as the graphics card has become more advanced it has taken some of the jobs previously assigned with the CPU and through a graphics pipeline adds 2D and 3D effects and it also adds textures.



The basic purpose of sound cards is to allow the user to hear sounds played by the OS and programs, along with music from audio CDs and other audio files, plus sound from DVD and other types of videos. In addition, these allow for voice communication using software such as Yahoo Messenger and Windows Messenger.

The sound card is an essential component in the PC, since it translates digital signals into analog audio for your listening pleasure. Well, that’s true, if you want to play games or run multimedia applications in your PC. Otherwise, it may not be necessary, especially in business environments.

With a sound adapter and appropriate software, a PC can perform various tasks, including:

  1. Playing audio CDs, either directly from a PC or from compressed digital copies of the CD soundtracks stored as MP3
  2. Playing stereo music, sound effects, and/ or voice prompts in games, education, training, and presentation software, as well as for operating system prompts, effort warnings, and other events.
  3. Capturing dictation to a document file, adding voice annotations to documents, or controlling applications using voice/ speech recognition software
  4. Supporting audio conferencing and telephony across a LAN or the Internet.
  5. Supporting text-to-speech software that allows the PC to “read” text aloud, aiding children who cannot read and people who are visually impaired.
  6. Creating and playing back music using MIDI software and hardware.



A modem is a device that connects a computer to a standard analog telephone line, the kind to which your telephone is connected.

A device that translates data from your PC into a form that can be sent to other computers over regular phone lines. The modem also receives signals from other computers and converts it into something your computer can understand. A modem is the device most home computers use to connect to the Internet. A Modem converts digital information into sound so that it may be transmitted over telephone lines. When the modem hears this sound on the other end it converts the sound back into digital information.


Types of Modems

There are two types of modems:

  • Internal.
  • External.


  1. Internal modems are PCI or ISA expansion cards. They tend to be simple to install; just follow the manufacturer’s directions if available. They receive their power from the slot. External modems are less common today, but are still around because internal modems are often optional these days.
  2. External modems traditionally plug into a serial port on the computer, although there are USB modems available today as well. The advantages of external modems are that you do not have to be a technician to install one and they can easily be moved from computer to another. The disadvantages of serial-port external modems are that they require external power and are more expensive. Most or all USB modems are powered by the USB ports and are not as expensive as serial port modems.



A network interface card, more commonly referred to as a NIC, is a device that allows computers to be joined together in a LAN, or local area network. Networked computers communicate with each other using a given protocol or agreed-upon language for transmitting data packets between the different machines, known as nodes. The network interface card acts as the liaison for the machine to both send and receive data on the LAN.

An Ethernet network interface card is installed in an available slot inside the computer. The NIC assigns a unique address called a MAC (media access control) to the machine. The MACs on the network are used to direct traffic between the computers. The back plate of the network interface card features a port that looks similar to a phone jack, but is slightly larger. This port accommodates an Ethernet cable, which resembles a thicker version of a standard telephone line. Ethernet cable must run from each network interface card to a central hub or switch. The hub or switch acts like a relay, passing information between computers using the MAC addresses and allowing resources like printers and scanners to be shared along with data.

A network interface card does not have to be hard wired with physical cable. Wireless Ethernet cards are installed like their wired counterparts, but rather than a port for an Ethernet cable, the card features a small antenna. The card communicates with the central wireless switch or hub via radio waves. Wireless LANs may have some restrictions depending on the material the building is made from. For example, lead in walls can block signals between the network interface card and hub or switch.



Input devices are devices that allow the user to input data into a computer. The most obvious input devices are Mouse and keyboards.

A) Keyboards: The keyboard is the main input device for most computers. There are many sets of keys on a typical “windows” keyboard. On the left side of the keyboard are regular alphanumeric and punctuation keys similar to those on a typewriter. These are used to input textual information to the PC.A numeric keypad on the right is similar to that of an adding machine or calculator.

Keys that are used for cursor control and navigation are located in the middle. Keys that are used for special functions are located along the top of the keyboard and along the bottom section of the alphanumeric keys.

Keyboards are mainly divided into two types:

  • Multimedia keyboard.
  • Ordinary Keyboard.


B) Mouse: Mouse is another input device used in computer. Mouse is a device that controls the movement of the cursor or pointer on a display screen.

A mouse is a small object you can roll along a hard, flat surface. Its name is derived from its shape, which looks a bit like a mouse, its connecting wire that one can imagine to be the mouse’s tail, and the fact that one must make it scurry along a surface. As you move the mouse, the pointer on the display screen moves in the same direction.

Mouse contain at least one button and sometimes as many as three, which have different functions depending on what program is running. Some newer mouse also includes a scroll wheel for scrolling through long documents.



A 3.5″ square holding a flexible magnetic disc that holds information or data. You need a floppy drive to read the floppy. A floppy disk can hold only 1.44 megabytes, but it is portable and allows you to make copies of your files.



A CD-ROM drive used to be an ‘optional extra’ in computers – it is no longer so. Most software packages come in CD format, so you must have a CD-ROM drive to read them. Typically, CD-ROM drives today need to be at least 24X speed to keep up with the newer software applications out there.

A CD drive connects to the computer motherboard through two types of cables. The older and more common connection is through the IDE Ribbon cable. Recently SATA (Serial ATA) drives have been produced and will gradually become more common. The benefits of having SATA cables is that they are smaller and the transfer rate is higher.

Floppy drives are the main source of data transfer and files which are small enough to fit on them. However, today even CD drives are getting out of date and are fast being replaced by the DVD ROM and DVD RW Drives.



CD writer is used to write CD. It can also be used as a CD drive. CD can write with different formats. By using CD writer we can be able to write with different speeds. Different types of writers are available in the market with different writing speeds.

On a CD drive there is usually some numbers with a x symbol after it. This stands for times, for example common speeds are 4x, 8x, 16x, 18x, 24x, 32x, 40x and 52x. CD RW drives have speeds like 24x-10x-40x or 52x-32x-52x.

When you are choosing one CD-RW you have to consider drive speed. For CD writers, you should generally look for a 40X record speed or faster. If you buy anything that is slower, it will definitely waste a lot of time when you are burning CDs.



A computer’s case is more than a box. The case includes the drive cage, the internal compartment that holds disk drives, and the power supply, among other features.

1) Cases: Most people think of a case as merely the enclosure that holds a PC together. That view is reasonable for people who buy a PC and never open the case, but anyone who builds or upgrades PCs soon realizes that all cases are not equally created.

The computer case is your computer’s housing. You need this to store your components, the largest of which is your motherboard. A good quality case can have a big impact on the performance and durability of the computer. Cases sold have to meet requirements for shielding against both external RFI and interference to external devices that is generated by the computer.

Good cases are designed to provide for proper airflow to keep the components from overheating. Well made cases do not have a thin tinny feel or sound when you tap on them. They have rolled edges to prevent injury. Panels should fit together well without requiring excessive effort. When the computer is running, a good case does not make excessive vibration noises. Other attributes of good cases include ease in opening and ease in accessing internal components.


Case Components

Cases come with various components, as shown in the figure below:

Most of these components are self-explanatory. Drive bays are areas in the front for installation of removable media (CD, DVD, floppy, Zip, etc.). The 5 1/4 inch bays are for all but the floppy drives. Cases usually come with small speakers, which are there to provide very basic sounds to the user. About all these speakers play are warning beeps and the sound of a modem connecting. These speakers are very important, because multimedia speakers do not work before Windows has booted, if Windows is in Safe Mode, or if there is a problem with the sound card.

While many older PCs had key locks, few newer ones do. Locking a computer prevents it from being powered on. The most important indicator lights are the ones that show that power is on and that the main hard drive is active. The hard drive indicator is helpful to show if the hard drive is running too much, or if the computer is locked up. On recent cases, the only button is the power button. Older cases might have a Reset button, which simply turns power off and on, and a “Turbo” button. Leave the Turbo button in the On position unless a tech support technician tells you to turn it off.


2) Power Supplies: A computer power supply is a compulsory unit to a computer. Without the power supply a computer is useless as it is just a case full of metal and plastic. This page will explain the different power cables and connectors and how they work inside your computer.

A power cable connects from the power point to the power supply where it supplies the motherboard and other components with power. Often there is a power switch on the back which can be switched off to stop the power current. If this is not switched off and even though the computer is off power will still be drawn out of the power point (in very small amount).

The most common power supply that we have in our computers today are the ATX Power Supply. The AT Power Supply was found in many computers a few years ago but this has become less common. The graphic below shows each power cable and its name.

The computer power supply is placed inside the computer case generally near the top of the case. It is sometimes necessary to buy a mini power supply for some cases are so small that they need one. Most computer cases when bought come with a power supply that is suited to its case. There are usually power ports on the motherboard for the fans in the case but if not it is possible to buy an adapter that will convert power from the 4-pin power cable to a fan power cable.



PCs use one of two monitor technologies: a traditional “glass bottle” CRT monitor or a flat-panel display (FPD) that uses LCD technology.

Monitor is the display device. Many times per second, the video card sends signals out to the monitor. The information video card sends controls which dots are lit up and how bright they are, which determines the picture you see.

Colour monitors can display anywhere from 16 to over 1 million different colors. Color monitors are sometimes called RGB monitors because they accept three separate signals -red, green, and blue.

The resolution of a monitor indicates how densely packed the pixels are. In general, the more pixels (often expressed in dots per inch), the sharper the image. Most modern monitors can display 1024 by 768 pixels, the SVGA standard. Some high-end models can display 1280 by 1024, or even 1600 by 1200.

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