Computer Hardware

Computer Hardware

1. Input and outpt devices

   • An input device is a piece of hardware that is used to enter data into a computer. There are two categories of input devices. Manual input devices and automatic input devices.
   • Types of input devices
     • The keyboard is the most common and widely used input device. It is made up of buttons called ‘keys’. The keys are arranged into sections • Alphabetical keys • Function keys or F keys (F1, F2, F3) • Numeric keys One set above the alphabetical keys the second a number keypad on the right hand side of a keyboard) • Arrow keys • Command keys (Insert, delete, home, end, page up/down) Most keyboards are called Qwerty keyboards. This name comes from the first six letters on the top row of the alphabet keys. Using a keyboard for too long can lead to health problems such as repetitive strain injury (RSI). To try and overcome this, different styles of keyboard have been developed, for example ergonomic keyboards. These are supposed to put your hands into a much more natural position than a traditional keyboard.
     • Along with the keyboard, it is one of the most common input devices you will use. A mouse is also called a ‘pointing device’ because it enables you to control what happens on the screen by moving the mouse on your desk and pointing, clicking and selecting items on the screen. A mouse usually has two buttons, a right and left one and also a central wheel which allows you to scroll up and down the page. The left and right buttons have different functions. Left clicking usually lets you put the cursor at a certain point on the page or let you choose a menu item. Right clicking brings you up a list of relevant menu items from which you can select a task. Many older styles of mice used a ball which moved against two internal rollers to record the direction that the mouse was being moved in. Modern versions of mice use ‘optical’ or ‘wireless’ technology to track mouse movement. If the mouse you are using now has a red light on the underside of it, it
   • Types of output devices
     • The most likely output from a system will be some form of visual message, text, images or video and that requires a monitor.
     • We often require some hard copy evidence and a printer is a common accessory to a computer system. There are a variety of types of printer including monochrome and colour laser printers for fast and economical output, or ink-jet printers, particularly useful for printing high quality images such as photographs. Supermarkets often have thermal printers built into their EPOS (Electronic point of sale) systems because they have fewer moving parts to cause problems and are virtually silent in use. In engineering design it is now quite common to have a 3D printer capable of producing a three dimension object based on a design. Architects often use large format plotters to produce plans.
   • Input devices for users with special needs
     • An eye-typer detects eye movement and blinking to input data
     • Puff-suck switch allow the user to operate switches by sucking or blowing into a tube.
     • Voice input is for those who find it difficult to operate a keyboard uses spoken commands to control the computer and attached devices
     • A joystick requires less physical movement than a mouse, so is an effective replacement for the mouse
     • Braille keyboard is for those with visual impairment. This is a specialist keyboard with raised patterns on the keys that match standard braille characters
     • Foot mouse is for those who have limited hand / arm movement a tracker-ball type of device operated with the foot.
   • Output devices for users with specific needs
     • Screen readers can be used to output the information on screen to aid those with a visual impairment.
     • Voice synthesisers provide spoken output from text input by a user who cannot communicate verbally.
     • Actuators provide physical movement in response to the computer and can be built into a range of devices to aid those with limited physical mobility.

2. Secondary Storage

   • Secondary storage is non-volatile disk space, and is sometimes called auxiliary memory, secondary memory or external memory.
   • RAM memory is volatile which means we will lose anything stored in RAM every time we turn off the computer.
   • ROM is not volatile but can only store pre-programmed sets of instructions so we are unable to save any changes or results.
   • Secondary storage is additional storage facilities added to a computer system to store data and programs when the power to a system is switched off.
   • All desktop computers and most other computer devices need some secondary storage to store the following items: • The operating system. • Any programs and applications that the user installs onto the computer. • Any files and documents containing the user’s data.
   • These cannot be stored in the primary memory. If they were stored in the ROM, they will not be alterable which means the user will not be able to install any programs or modify any files. If they were stored in the RAM, they will be lost every time the computer is switched off.
   • Internal and removable storage
     • Internal storage devices are built into the computer. They are always used with only one computer so they store programs and data used on that computer.
     • Removable storage (External memory) this can be used on more than one computer unlike internal storage
     • Magnetic Hard Drives is the mostly used secondary storage device. It is a magnetised rigid plate or stack of plates with heads to read the data as the platters spin around. They spin at around 7200rpm. The data is encoded into bits and written onto the surface as a series of changes in the direction of the magnetisation. The data is read by detecting the changes in direction.