Computer Hardware

Computer hardware refers to the physical parts or components of a computer such as monitor, keyboard, computer data storage, hard drive disk, mouse, system unit (graphic cards, sound cards, memory, mother board and chips), etc. all of which you can actually touch. Computer hardware is the physical components (devices), which are the building blocks of personal computers. These are installed into a computer case, or attached to it by a cable or through a port. In the latter case, they are also referred to as peripherals. A combination of hardware and software forms a usable computing system.

Hardware of a modern personal computer:

  1. Monitor
  2. Central Processing Unit Memory
  3. Memory
  4. Storage Devices
  5. Video Card
  6. Sound Card
  7. Ports

Basics of Computer Hardware that runs inside your computer:

Personal Computer Case: A computer case also known as a “computer chassis”, “tower”, “system unit”, “base unit” or simply “case” and sometimes incorrectly referred to as the “CPU” or “hard drive” is the enclosure that contains most of the components of a computer (usually excluding the display, keyboard and mouse).

Cases are usually constructed from steel (often SECC – Steel, Electro galvanized, Cold-rolled, and Coil) or aluminum. Plastic is sometimes used, and other materials such as glass, wood and even Lego blocks have appeared in home-built cases.

Hardware Components:

1  Monitor:

There are two types of monitors available for PCs: The traditional CRT (cathode ray tube) and The newer LCD (liquid crystal display).

  • The CRT is used for both televisions and computers. It produces a good quality image at a number of different settings for a reasonable price.
  • LCD monitors, also known as flat panel displays, are used in laptop (or notebook) computers and more frequently for desktops as well.
  • They are lighter and smaller (only inches thick) than CRTs with reduced electromagnetic emissions and power consumption.
  1. CPU (Central Processing Unit):

The CPU (Central Processing Unit), a complete computation engine that is fabricated on a single chip, is the computer’s brain. It is sometimes referred to as the central processor, microprocessor, or just processor.

Two typical components of a CPU are:

  1. The arithmetic logic unit (ALU), which performs arithmetic and logical operations,
  2. The control unit, which extracts instructions from memory and decodes and executes them, calling on the ALU when necessary.

The speed of processors, called the clock speed, is measured in megahertz (MHz) or gigahertz (1 GHz = 1000 MHz). One MHz represents one million cycles per second. For example, a processor that runs at 200 MHz executes 200 million cycles per second. Each computer instruction requires a fixed number of cycles, so the clock speed determines how many instructions per second the microprocessor can execute. To a large degree, this controls how powerful the processor is.

3 Memory:

ROM (Read Only Memory) : It is the computer’s permanent, long-term memory. It doesn’t disappear when the computer is shut off. It can not be erased or changed in anyway. However, there are types of ROM called PROM that can be altered. The P stands for programmable. ROM’s purpose is to store the basic input/output system (BIOS) that controls the start-up, or boot process.

RAM (Random Access Memory): It is a working area where the operating system (e.g. Windows), programs and data in current use are kept, ready to be accessed by the processor. It is the best known form of computer memory. However, RAM, unlike ROM, is emptied when the computer is switched off. The more RAM you have, the quicker and more powerful your computer is.

There are two basic types of RAM: dynamic RAM (DRAM) and static RAM (SRAM).

  • The two types differ in the technology they use to hold data.
  • DRAM, the more common type, needs to be refreshed thousands of times per second.
  • SRAM does not need to be refreshed, which makes it faster, but it is also more expensive than DRAM.

Memory is measure in the following units:

–  1 byte = 8 bits (Each 1 or 0 is called a bit (i.e. binary digit). Each character (i.e. a letter, a number, a space, or a punctuation mark) has its own arrangements of 8 bits, e.g. 01000001 = “A”, 01000010 = “B”.

–  1 KB (kilobyte) = 1024 (210) bytes

–  1 MB (megabyte) = 1024 (210) KB

–  1 GB (gigabyte) = 1024 (210) MB


Cache (pronounced as “cash”) is a buffer (made of a small number of very fast memory chips) between main memory and the processor.

  • It temporarily stores recently accessed or frequently-used data. Whenever the processor needs to read data, it looks in this cache area first.
  • If it finds the data in the cache, then the processor does not need to do more time-consuming reading of data from the main memory.
  • Memory caching allows data to be accessed more quickly.
  1.  Storage Devices:

The most common forms of storage devices in a home computer are:

– Hard disk drive

– Floppy disk


– CD-R and CD-RW


– USB flash drives

1) Hard disk and hard drive (HD):

A hard disk is a magnetic disk on which you can store computer data on a more permanent basis. The term “hard” is used to distinguish it from a soft, or floppy, disk.

  • Hard disks hold more data and are much faster than floppy disks and optical disks. A hard drive is a mechanism that reads and writes data on a hard disk.
  • The capacity of hard drives in newer PCs ranges from 20GB to 60GB in size since all software, from operating systems to word processors, and media files have grown tremendously in size over the last few years.

2) Floppy disk and floppy drive

A floppy disk (often called floppy or disk) is a soft magnetic disk and a floppy drive is a mechanism that reads and writes data on a floppy. Unlike most hard disks, floppy disks are portable, because you can remove them from a disk drive.

  • Floppy disks are slower to access than hard disks and have less storage capacity, but they are much less expensive.
  • The common size of floppies for PCs made before 1987 was 5¼ inches. This type of floppy was generally capable of storing between 100KB and 1.2MB of data.
  • After 1987 the size reduced to 3½ inches, but the data storage capacity increased, from 400KB to 1.44MB.
  • The most common sizes for PCs are 720KB (double-density) and 1.44MB (high-density).

3) Optical disk and optical drive:

Optical disks can store information at much higher densities than floppy disks. Thus, they are ideal for multimedia applications where images, animation and sound occupy a lot of disk space.

  • Besides, they are not affected by magnetic fields. This means that they are secure and stable.
  • for example, they can be transported through airport metal detectors without damaging the data. However, optical drives are slower than hard drives.

There are various types of optical disks and drives:

  1. A) CD-ROM (short for “Compact Disk-Read-Only Memory”) and CD-ROM drive:

A CD-ROM, an optical disk onto which data has been written via a laser, can store everything, from shareware programs to dictionaries and encyclopedias, from multimedia databases to 3-D games.

  • CD-ROMs are considered the most economical devices of storing and sharing information.
  • For example, a CD-ROM (700 MB) can replace 300,000 pages of text (about 50 floppies), which represents a lot of savings in distributing materials and data.
  • Yet, you can only read information on a CD-ROM but cannot write anything on it.

A CD-ROM drive is used to play CD-ROMs and it can also play audio CDs. CD-ROM drives are available in a variety of different speeds, the speed being described thus: 12x, 16x, 24x, 32x, 48x, etc.

  • This indicates the speed at which data can be pulled off the CD-ROM drive. Higher-speed  CD-ROM drives help to transfer data more quickly, which is crucial when playing sound or video.
  1. B) CD-R, CD-RW and CD-R/CD-RW drive (also called CD-burner or CD-Recorder):
  • CD-R (short for “Compact Disk Recordable”) drives record data on CD-R disks (but write once only), allowing you to create and duplicate CD-ROMs and audio CDs. They can also be used to back up hard disks or to distribute and archive information.
  • CD-RW (short for “Compact Disk Rewritable”) drives can erase and reuse data on CD-RW disks. In fact, to create CD-ROMs and audio CDs, you’ll need not only a CD burner, but also a CD-R/CD-RW software package.
  1. C) DVD-ROM (“DVD” is short for “digital video disk” or “digital versatile disk”):

A DVD-ROM (or just DVD) is a type of optical disk technology similar to the CD-ROM. It can hold up to 17 GB of data, about 25 times an ordinary CD-ROM.

  • For this reason, a DVD-ROM can store a large amount of multimedia software and complete movies in different languages.
  • It can also play music CDs and CD-ROMs. DVDs are read-only devices.
  • To avoid this limitation, companies also produce DVD-R/DVD-RW disks and DVD-burners.

4) USB flash drive

A USB flash drive is a small, portable flash memory card that plugs into a computer’s USB port and functions as a portable hard drive with up to 2GB of storage capacity. USB flash drives are easy-to-use because they are small enough to be carried in a pocket and can plug into any computer with a USB drive. In addition, they are very durable because they do not contain any internal moving parts. USB flash drives also are called pen drives, key drives, or simply USB drives.

5  Video Card:

The card here is a jargon for an electronic circuit board. Video cards are also known as graphics cards, which are responsible for displaying 2D and 3D images on your monitor. 2D graphics are the regular pictures and images that appear on your screen while 3D graphics are mostly used in games and imaging.

  • Video cards control the resolution of the text, pictures and video that appears on the screen, i.e. the screen resolution (e.g., 800 x 600 pixels, 1024 x 768 pixels).
  • Most modern video cards are accompanied by the software that enables you to control the resolution of the display screen according to the software that you are using.
  • The lower the numbers, the lower the resolution.
  • Remember that getting the video card setting wrong is a common reason for failing to get software to work properly.

6  Sound Card

A sound card is an electronic circuit board that is mounted inside the computer to control sound output to speakers or headphones, to record sound input from a microphone connected to the computer, and to manipulate sound stored on a disk. Sound cards are essential for multimedia applications and have become common on modern personal computers.

  • A popular make of soundcard is SoundBlaster, which has been the de facto standard sound card.
  • Most sound cards in the past have beenSound Blaster-compatible, which means that they can process commands written for a Sound Blaster card, because most programs that use a sound card have been designed that way.
  • Nowadays, many sound cards are also Windows-compatible.
  • Many multimedia applications require the system to have a Windows-compatible sound card to run properly.

7  Ports

A port is an interface on a computer to which you can connect a device. Personal computers have various types of ports. Internally, there are several ports for connecting disk drives, monitors, and keyboards. Externally, personal computers have ports for connecting modems, printers, mice, and other peripheral devices.


There are three common types of external ports that usually come with a computer:

1) Parallel ports (for most printers)

2) Serial ports (for most modems and some mice)

3) USB (Universal Serial Bus) ports (for about every peripheral made in a USB version)

Note: A “bus” is a set of conductors that carry signals between different parts of a computer


The USB (Universal Serial Bus) provides a single, standardized, easy-to-use way to connect up to 127 devices to a computer. USB:

  • The USB connectors let you attach everything from mice to printers to your computer more quickly and easily than the other two.
  • The operating system supports USB as well, so the installation of the device drives is quick and easy, too.


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