Definition of a Computer

A computer can be defined as an electronic device that receives input from the user through a mouse or keyboard, processes it in some fashion and displays the result on a screen. It can also be assumed as any device that has a microprocessor in it.

Types of Computers

Fundamentally, there are two types of computers

  • analog
  • digital

Analog computers solve problems by using continuously changing data such as

  • temperature
  • pressure
  • voltage

Digital computers solves problems by manipulating discrete binary digits (1s and 0s).

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3 Main Types of Computers

  • mainframes
  • minicomputers
  • microcomputers

They differ in size, speed of operation, amount of data that can be stored, and the number of simultaneous users.

  1. microcomputers
  2. minicomputers
  3. mainframe computers

personal or desktop computer designed for general use by a single person
mid-range servers supporting smaller number of simultaneous users, typically 50 to 100
allow many simultaneous users

home and all types of businesses
larger businesses
industry, research, and university computing centers

entertainment, communication, personal databases, and spreadsheets, word processing, accounting, inventory control, research
accounting, billing, and inventory records
typically huge databases, complex mathematical operations, processing millions of transactions everyday.

Types of Computers Based on Size

Desktop– A Personal Computer that is not designed for portability. The computer is set up in a permanent location. Most desktops offer more power, storage and versatility for less cost.

Laptop– These are also called notebooks. Laptops are portable computers that integrate the display, keyboard, a pointing device or trackball, processor, memory and hard drive all in a battery-operated package slightly larger than an average hardcover book.

Palmtop– More commonly known as Personal Digital Assistants (PDAs)

  • Palmtops are tightly integrated computers that often use flash memory instead of a hard drive for storage
  • These computers usually do not have keyboards but rely on touch screen technology for user input
  • Palmtops are typically smaller than a paperback novel, very lightweight with a reasonable battery life. A slightly larger and heavier version of the palmtop is the handheld computer.

Workstation– A desktop computer that has a more powerful processor, additional memory and enhanced capabilities for performing a special group of task, such as 3D Graphics or game development.

Server– A computer that has been optimized to provide services to other computers over a network. Servers usually have powerful processors, lots of memory and large hard drives.

Supercomputer– This type of computer usually costs hundreds of thousands or even millions of dollars. Although some supercomputers are single computer systems, most are comprised of multiple high performance computers working in parallel as a single system. The best known supercomputers are built by Cray Supercomputers.

Wearable– The latest trend in computing is wearable computers. Common computer applications (e-mail, database, multimedia, calendar/scheduler) are integrated into watches, cell phones, even clothing!

Basic Units of a Computer

Modular units usually consist of the following separate components:

  • The Computer
  • The Monitor
  • The Keyboard
  • The Mouse
  • Peripherals

Central Processing Unit (CPU)

Central processing unit (CPU):The heart of the computer, this is the component that actually executes instructions organized in programs (“software”) which tell the computer what to do.

Storage Devices

Memory(fast, expensive, short-term memory):Enables a computer to store, at least temporarily, data, programs, and intermediate results.

Mass storage device (slower, cheaper, long-term memory): Allows a computer to permanently retain large amounts of data and programs between jobs. Common mass storage devices include disk drives and tape drives.

Input Devices

  1. Keyboard
  2. Mouse
  3. Tracker ball
  4. Joystick
  5. Light pen
  6. Digital Camera
  7. Microphone
  8. Touch screen
  9. Video Digitizer
  10. Graphics tablet
  11. Scanner
  12. OCR (Optical Character Recognition)

Output Devices

  1. Monitors or Visual Display Units (VDUs)
  2. Printers
  3. Plotters

Other devices

  1. Speakers
  2. LCD projectors
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