Computer Systems

Note to the student Please make brief notes on the following computer hardware + software components After each section research the current standards of performance + price. Get the best of everything

Using a computer system A computer system involves the same process: data is input, processed, stored and then output. Figure 2.2 shows the steps in using a computer to complete a task. A computer system consists of input devices, a computer processor, a storage device and output devices. The computer system is made up of both hardware and software.

What makes up a computer? Hardware Hardware consists of the parts you can actually touch, hold and move (with care). This includes the central processing unit (CPU), monitor, keyboard and a mouse or pointing device. Other pieces of hardware that can be attached to a computer are called peripheral devices—these include printers, disk drives, scanners, digital cameras, compact disc (CD) drives and digital video (DVD) drives.

Software Software is made up of a series of instructions that tell the hardware what to do.The sequence of instructions is called a computer program. You cannot see or touch computer software. It is stored as electronic impulses on disk.Each computer has an operating system. This software makes the computer usable—it provides a link between the hardware and the person using the computer. When the computer is turned on, the operating system starts up the computer.

Central processing unit (CPU) The central processing unit (CPU) is the part of the computer system where all calculations and instructions are carried out. The CPU controls the performance of all other parts of the computer. The CPU is usually a silicon chip—that is, a small device made of silicon on to which a circuit is printed using a photographic process.

Random access memory (RAM) Computer memory refers to the internal part of the computer used to store instructions and data. When an application is run, instructions are loaded into random access memory (RAM). Each application requires some of the RAM to work effectively. The amount of memory is measured in kilobytes (KB) and megabytes (MB). One MB is equal to 1024 KB. A typical personal computer has a minimum of 256 MB of RAM.

Read-only memory (ROM) This part of the computer is where essential instructions and data for the operating system are recorded. The data may be accessed but not altered by the user—that is, it can be looked at but not changed. When a computer starts up, it first accesses instructions stored in a read-only memory (ROM) chip.

Monitor A computer monitor is the screen the computer uses to display input and output. Colour monitors display a minimum of 256 colours, although some display several million. Flat screen monitors use less desk space and are easier to read than CRT monitors.

A keyboard is the most common device used for entering data. Most computers have a standard ‘QWERTY’ keyboard that has its origins in the typewriter. ‘QWERTY’ refers to the six characters on the top left-hand side of the keyboard. When a key is pressed, it is translated into an instruction the computer can understand. A mouse is a pointing device used to control the cursor and to help move around a computer screen. It can be used to carry out commands by pointing and clicking the mouse buttons. The standard Windows mouse has two buttons. Many models also have a wheel. A mouse can be connected to a computer using a cable, usually USB. They can also be connected wirelessly using: Infrared Bluetooth.

What can be attached to a computer? A peripheral device is anything external to the computer that can be attached to the computer. Peripheral devices include: printers external disk drives scanners microphones CD (compact disc) drives modems video cameras CD writers DVD (digital versatile disk) writers.

Input/output devices The devices listed above can all be used as either input or output devices. An input device is used to transfer data into a computer. For example, a scanner can be used to enter data in the form of a diagram or a photograph. A microphone can be used to enter sounds. An output device is used to present data that is transferred from a computer. A printer is used to display a letter or essay that has been written using a computer. Speakers can play sounds that have been recorded on a computer. A monitor can display a presentation.