Classifies computers using a verity of methods
Computers designed by using the binary digital number system are called digital computers which can count and accept numbers and letters through various input devices.
- Advantage – high accuracy, most suitable for business applications,
- Disadvantage – high cost, regular reductions in price, complexity of programming
Computers which are designed considering the physical data (භෞතික දත්ත) such as voltage/වෝල්ටීයතාව, resistance/ප්රතිරෝධය, temperature/උෂ්ණත්වය, thrust/බලය, and pressure/පීඩනය are called the analog computers which process data input in a continuous form (unbroken flow of information).
- Advantage – low cost, easy of programming, uses for engineering and scientific applications.
- Disadvantage – accuracy factor, limited storage capacity, not suitable for processing business data.
A computer can also be built using some part employing digital components and some parts based on analog principles . A combination of the above two types of computers can be called hybrid computers.
- Advantage – process of both analog and digital methodologies.
- Supercomputers are used to get very special work done. A parallel functioning of several super computers can be seen mostly. These are the largest and fastest computers available but are typically not used for commercial data processing.
- Instead they are used in specialized area as in Defense, Aircraft design, computer generated movies, weather research etc.
- Supercomputer can process 64 bits or more at a time. Their processing speed ranges from 10.000 million instructions per second to 1.2 billion MIPS. They can support 10.000 terminals at a time. They have huge numbers of storage and other devices connected to them.
- Eg:- ILLIAC IV, CRAY, CDC, FUGITSU, NEC, CRAY-1, CRAY-2, CRAY-3
- Mainframes are less powerful and cheaper than supercomputers. These computers are very large in size and can be hardly seen today.
- They are big general purpose computers capable of handling all kinds of scientific and business applications. They are used for such application as payroll computations, accounting, business transactions, information retrieval and airline seat reservations.
- Mainframe can process several MIPS. More than 1000 remote terminals can be supported and have large on-line secondary storage capacity.
- Eg:- ES/9000
- Medium size computers can be called minicomputers. This type of computer performs data processing activities in the same way as the Mainframe but not on a smaller scale. The cost of minis is lower. A mini computer can typically support 10 to 12 terminals.
- Eg:- NOVA, DEC, PDP_II and IBM series.
- Extremely small computers can be called microcomputers which consisting of a microprocessor and associated storage and I/O devices. They are also called Personal Computer systems. Microcomputers were first available for widespread use in the 1970′s. When became possible to put entire circuitry (CPU) in a small silicon chip.
Classifies computers peripherals by function
- CD/DVD ROM Drive
- Hard Disk Drive (HDD)
- Floppy Disk Drive (FDD)
- Graphics tablet
- Computer Monitor
- Computer Mice
- Digital Camera
- Web Camera
- PC Speaker
- Light Pen
- Joy stick
The part of the computer that we come into contact with most is probably the piece that we think about the least. But the keyboard is an amazing piece of technology.
- 101-key Enhanced keyboard
- 104-key Windows keyboard
- 82-key Apple Standard keyboard
- 108-key Apple Extended keyboard
The typical keyboard has four basic types of keys:
- Typing keys (A, a, …)
- Function keys (F1, F2, …)
- Numeric keypad (17 keys) (0, 1, 2, /, *, +, -, …)
- Control keys [Enter, Homes, End, Insert, Delete, Page Up, Page Down, CTRL, Shift, Alt, Esc, ...]
The most common keyboard layout is QWERTY. Other type of keyboard is Dvorak.
A computer display is a marvelous thing. An unassuming dark gray surface can suddenly transform into an artist’s canvas, an engineer’s gauge, a writer’s page or your very own window to both the real world and a huge range of artificial worlds.
- Cathode Ray Tube / CRT – Most desktop displays uses a CRT.
- Liquid Crystal Display / LCD – Portable computing devices such as laptops incorporate LCD.
- Light Emitting Diode / LED – A display technology that uses a semiconductor diode that emits light when charged with electricity.
The copies taken from the printer are called hard copies and the copies shown on the monitor are called soft copies. As far as technology is concerned, printers can be mainly divided into two.
- Impact (ඝටන) printers.
- Wheel Printer
- Dot Matrix Printer
- Line Printer
- Non-impact (නොඝටන) printers
- Ink Jet or Bubble Jet printers
- Laser printers
- Thermal printers
- Dye Sublimation printers
Purchasing and Operating Price – A low purchase price will usually mean high operating cost. If a company is looking for a high-performance printer, the printer’s operating costs will be decisive in their choice.
This is an input device that can convert a hard copy into a soft copy. Scanner is used to feed pictures, images or texts to the computer. Further, the facility of Optical Character Recognition (OCR) is used to insert Texts
- Flatbed/desktop scanner – are most versatile and commonly used scanners.
- Sheet-fed scanner – looks a lot a small portable printer.
- Handheld scanner – rely on the user to move them instead of a motorized belt.
- Drum scanner – are used by the publishing industry to capture incredibly detailed image. They use a technology called a photomultiplier tube (PMT).
Identify and connects basic peripherals to the computer
- A system unit has jack points. Some jack points have symbols some jack points have pins and some have holes.
- Jack points are called ports. Ports are used to connect peripherals to the computer.
- There many types of ports. Symbols help to identify the relevant peripheral.
- Male ports have pins. Female ports have holes.
- PS/2 ports are used to connect the mouse and keyboard.
- A VGA (Video Graphics Array) port is used to connect the monitor or Multimedia Projector.
- Parallel port is used to connect external devices such as printers and scanners.
- A Universal Serial Bus (USB) port can be used to connect all kind of external devices, such as external hard drives, printer, pen drive, mice, keyboards, scanners.
- The Ethernet (RJ-45 (Registered Jack 45)/Network) port is used to connect the computer to a network or to internet.
- A Serial port is used to connect external modems or an older computer mouse to the computer.
- Modem Port (RJ-11) MODEM device is used to connect the computer to Internet and also to send faxes using the computer in the computer are called Internal MODEMS while the MODEMS fixed outside the computer are called External MODEMS.
- The regulated power supply inside the computer transforms mains electricity into DC current used in the computer. It as an internal fan to cool the unit.
Uses basic block diagram to demonstrate the computer system
Five basic functions can be identified which are done by the computer. Those are;
- Input or inserting data and instruction/ දත්ත සහ උපදෙස් ආදානය/ඇතුළත් කිරීම – Input can be defined as inserting data and instructions needed for a computer.
- Processing / දත්ත සැකසීම – The process of converting data inserted to the computer to information as required can be defined as processing.
- Output or retrieving data or information / තොරතුරු ප්රතිදානය කිරීම – Giving the processed data and information to the external forces is done under Output.
- Storing data or information / දත්ත ගබඩා කිරීම – Data and information are stored in a way that those can be reused later as required. This is done under Storing.
- Controlling / පාලන කටයුතු – The process of a computer system should be controlled properly. This controlling done to a computer system is considered here.
Computer is made of four main parts. Those are;
1. Input Devices /ආදාන උපක්රම
2. Output Devices / ප්රතිදාන උපක්රම
3. Central Processing Unit [CPU] / සකසනය
4. Storage Devices / ගබඩාකරණ උපක්රම