Read Only Memory (ROM)

As RAM is volatile, the computers need a non-volatile memory to read larger programs. This is known as the Read Only Memory (ROM). The programs which are needed to start up your computer (Ex: to boot the computer) are stored in ROM.

Cache. Most of todays computers improve their processing times by using cache (pronounced cash).

Memory cache, also called a cache store or RAM cache, helps speed the processes of the computer by storing frequently used instructions and data thus reducing the access time of data. When the processor needs an instruction or data, it first searches in the cache.

 

Input Devices. A computer executes instructions and processes data into information and stores the information for future use. Input devices are used to enter instructions and data into the computer.

What is Input? Input is any data or instructions you enter to the memory of a computer. Once input is in memory, the CPU can access it and process the input into output. There are four types of input namely: data, programs, commands, and user responses.

Data. Data is a collection of unorganized facts that can include words, numbers, pictures, sounds, and videos. A computer manipulates and processes data into information, which is useful.

Program. A program is a series of instructions that tells a computer how to perform the tasks necessary to process data into information. Programs are kept on storage media such as a floppy disk (not used now), hard disk, CD-ROM, or DVD-ROM. Programs respond to commands issued by the user.

Command. A Command is an instruction given to a computer program. Commands can be issued by typing keywords or pressing special keys on the keyboard. A keyword is a specific word, phrase, or code that a program understands as an instruction. Some keyboards include keys that send a command to a program when you press them. Instead of requiring you to remember keywords or special keys, many programs allow you to issue commands by selecting menu choices or graphical objects. For examples, programs that are menu driven provide menus as a means of providing commands. Today, most programs have a graphical user interface (GUI) that uses icons, buttons, and other graphical objects to issue commands. However, GUI is the most user friendly way to issue commands

Input Devices

An Input Device is any hardware component that allows you to enter data, programs, commands, and user responses into a computer. Some of the commonly used input devices are listed below.

Keyboard

Pointingdevices

• Mouse

• Trackball

• Joystick

• Touchpad

• LightPen

Scanners

Voiceinputsystems

WebCam

Barcodereaders

Output Devices.

An output device is any computer component capable of conveying information to a user. Some commonly used output devices are listed below.

Display devices

Cathode Ray Tube (CRT) monitors

Liquid Crystal Display (LCD) monitors / Flat-panel displays

LED Monitors

Gas plasma monitors

Printers

- Impactprinters

- Daisy Wheel and Dot Matrix printers

Non-ImpactPrinters

- InkJetprinters

- ThermalDyeTransferprinters

- Laserprinters

Plotters

AudioDevices

Speakers

Headphones

Monitor. The monitor displays the output to the user visually. Therefore it is also called the Visual Display Unit (VDU) or simply the screen. Similar to televisions, the sizes of monitors are varying and often expressed in diagonally measured distance in inches. The technology used with monitors is expanding rapidly and there are two major types of monitors that differ in the technology of visualizing the output to the user. They are Cathode Ray Tube (CRT) monitors, Liquid Crystal Display (LCD) and Light Emitting Displays (LED).

The CRT monitor has more lines of dots per inch, higher the lines more amount of the resolution. It creates the picture by number of rows or lines of the small tiny dots. For an instance the resolution of 1024 x 768 will be sharper than 800 x 600 resolutions.

The LCD consists of two sheets of polarizing material with a liquid crystal solution between them. When an electric current passed through the liquid crystal solution, crystals align so that light cannot pass through them. It is like a shutter either allows light to pass through or blocking the light.

The LED is the latest marketing innovation of display units. It looks similar to LCD and it is also a flat panel display. LED means Light Emitting Diode and relates to the way the display is illuminated. LED monitors still use the same Liquid Crystals as the previous LCD displays. The way the backlight works however with the LED's will lead to a number of improvements in the display.

Though CRT monitors are much cheaper than LCDs and LEDs, the CRTs consume more power than others

Printer. A computer printer produces a hard copy (permanent human-readable text and/or graphics) of documents stored in electronic form, usually on physical/tangible print media such as paper or transparencies. Many printers are primarily used as local computer peripherals, and are connected by a printer cable to a computer which serves as a document source. Some printers, commonly known as network printers can serve as a hardcopy device to be shared and used by any user among a group of users connected to the network. Individual printers are often designed to support both local and network connected users at the same time. There are several types of printers categorized based on the applied technology of printing text/graphics on the paper.

Impact Printers. Any impact printer forms characters and graphics on a piece of paper by striking a mechanism against in an ink ribbon that physically contacts the papers. Because of the striking activity, impact printers generally are noisy.

Many impact printers do not provide letter-quality print. Letter-Quality (LQ) output is a quality of print acceptable for business letters. Many impact printers produce near letter-quality (NLQ)

print, which is slightly less clear than LQ. NLQ impact printers are used for jobs that require only NLQ, such as printing of mailing labels, envelopes, or invoices.

Impact printers are also ideal for printing multipart forms because they easily can print through many layers of paper. Finally, impact printers are used in many factories and retail counters as they can survive in dusty environments, vibrations, and extreme temperatures.

Plotter. Plotters are special type of printers used to print graphicaloutput on paper. It interprets computer commands and makes line drawings on paper using ulticolored automated pens.

Storage Devices. Storage refers to the media on which data, instructions, and information are kept, as well as the devices that record and retrieve these items. In this section we will discuss about the storage media and storage devices.

Memory versus Storage. It is important to understand the difference between the memory. Memory holds data and instructions temporarily while they are being processed by the CPU. Storage, also called Secondary, Auxiliary storage, or Mass storage, holds items such as data, instruction, and information for future use.

Storage. Storage is non-volatile which means that items in storage remains even when power is removed from the computer. A storage medium is the physical material on which the items are kept. One commonly used storage medium is a disk, which is round, flat piece of plastic or metal with a magnetic coating on which items can be written. A storage device is the mechanism used to record and retrieve items to and from a storage medium.

Storage devices can function as source of input and output. For example, each time a storage device transfers data, instructions, and information from a storage medium into memory (a process called Reading); it functions as an input source. When a storage device transfers these items from memory to a storage medium (a process called Writing), it functions as an output source.

The speed of a storage device is defined by its access time, which is the minimum time it takes the device to locate a single item on the disk. Compared to memory, storage devices are slow. The access time of memory devices are measured in milliseconds.

Hard Disk. Hard Disk drive which is often referred to as Hard Disk or Hard Drive is a device to store and retrieve data in a computer. The hard drive can store important system files like the operating system, program files and other data. Though HDDs were originally designed to be used with computers nowadays the applications for HDDs have expanded beyond computers to include digital video recorders, digital audio players, personal digital assistants, digital cameras and video game consoles. HDD is a non-volatile storage device that stores digitally encoded data. It is an electromagnetically charged surface or set of disks that record data in concentric circles known as tracks. HDDs record data by magnetizing ferromagnetic material directionally, to represent either a 0 or a 1 binary digit. They read the data back by detecting the magnetization of the material. A typical HDD design consists of a spindle which holds one or more flat circular disks called platters, onto which the data is recorded. The platters are made from a non-magnetic material, usually aluminum alloy or glass, and are coated with a thin layer of magnetic material.

Portable Hard Disks. Portable hard disk is an interesting and useful device because you can carry data about all over the place and transfer information, programs, pictures, etc. between computers. Modern portable hard disks have a massive capacity like 500GB.

The System Unit. Т he System Unit of the computer is the box-like casing which contains the major electronic components that are responsible for the main functions of the computer. It should be mentioned here that many people use to refer to this as the CPU incorrectly. This erroneous reference may be due to CPU: The brain of the commuter being that significant. However, the electronic devices such as CPU, memory, hard disk drive are located inside the System Unit. In addition to the above parts, Motherboard, Floppy DiskDrive, Power Supply unit, and CD-ROM Drive are the other major components that youcan find within the system unit. A brief description of each above component is given next.

Motherboard. The motherboard is sometimes called the system board, planner board or main board. It is the main circuit board of a computer. The motherboard contains several connectors for attachingadditional boards. Usually, the motherboard contains the CPU, BIOS, memory, mass storage interfaces, serial/parallel ports, expansion slots, and all the controllers required to control standard peripheral devices, such as the display screen, keyboard, and disk drive.All of the basic circuitry and components required for a computer to function are onboard the motherboard or are connected with a cable. The most important component on a motherboard is the chipset. It often consists of two components or chips known as the Northbridge and Southbridge, though they may also be integrated into a single component. These chips determine, to an extent, the features and capabilities of the motherboard.

Power Supply Unit. Power Supply Unit (PSU) is another very important unit found in the system unit. Usually we connect the power code of the computer to the domestic mains supply. Therefore, PSU converts Alternating Current (AC) from mains supply to Direct Current (DC) with the required different voltages needed to power different components of the computer. Power supplies have a certain power output specified in Watts, a standard power supply would typically be able to deliver around 350 Watts. The more components like HDD, CD/DVD drives, and cooling fans, are connected to your computer the greater the power required fro m the power supply

CD-ROM Drive. The CD-ROM drive is a high capacity optical data storage device with a removable disk, it writes data onto or reads data from a storage medium.

A CD-ROM drive may be connected to the computer via an IDE (ATA), SCSI, S-ATA, Firewire, or USB interface or a proprietary interface

 

Questions:

1. Why does a computer need memory?

2. What is the best type of storage for my data?

3. What factors affect a computer’s screen display?

4. Are ink jet printers better than laser printers?

5. What’s the best way to add devices to a computer system?

6. How can I protect my computer system from theft and damage?

 

References

1. June J. Parsons and Dan Oja, New Perspectives on Computer Concepts 16th Edition - Comprehensive, Thomson Course Technology, a division of Thomson Learning, Inc Cambridge, MA, COPYRIGHT © 2014.

2. Lorenzo Cantoni (University of Lugano, Switzerland) James A. Danowski (University of Illinois at Chicago, IL, USA) Communication and Technology, 576 pages.

3. Craig Van Slyke Information Communication Technologies: Concepts, Methodologies, Tools, and Applications (6 Volumes). ISBN13: 9781599049496, 2008, Pages: 4288

4. Utelbaeva A.K.,Utelbaeva A.K. Study guide for lectures on discipline “Computer science”, Shimkent 2008, 84 pages.