1. Supercomputer

1. 
   Types of computers
   

There are 5 broad types of computers:


1. Supercomputer: These are very high-capacity computers with hundreds of processors that collectively perform over 1 trillion calculations per second. They are used primarily for research purposes, airplane design, oil exploration, weather forecasting, and other activities that cannot be performed effectively by less
powerful machines. Large government installations, multinational enterprises (MNEs), and entertainment industries like Hollywood are the most likely users of supercomputers. Leading brands of supercomputers include Cray, Fujitsu and NEC.
2. Mainframe computer: Water- or air-cooled computers that varies in size from small, to medium, to large, depending on their use. Able to support hundreds and even thousands of users simultaneously. Mainframes are used by large organisations like banks, airlines, insurance firms, colleges and the government that need to process millions of transactions. A recent application of the mainframe is in e-commerce, where it is deployed as a e-commerce server used to process online orders and payments. A leading brand of mainframes is IBM.
3. Minicomputer: A mid-size version of the mainframe, minicomputers usually have multiple terminals attached. They may be used as network servers and Internet servers in large organisations.
4. Workstation: these are powerful computers that are usually used for complex scientific, mathematical, and engineering calculations. They may also be used for specialised tasks like computer-aided design/computer-aided manufacturing and multimedia designing. Workstations are used for such tasks as designing automobile engines, prescription drugs, and movie special effects. A leading manufacturer of workstations is Sun Microsystems in the US.

5. Microcomputers (PC):
- Desktop computer: Horizontal case or main housing that sits on the desktop. It could be used at home or the office.
- Tower: Case sits in a vertical tower on the floor or desk.
- Notebook/Laptop: a lightweight and portable computer that comes with integrated monitor, keyboard, hard-disk drive, CD-ROM drive, and battery. Many people need a computer in a variety of setting – at work, at home, at school. Instead of buying a desktop computer for each place, people own one notebook computer that they can take with them wherever they go.
- Personal digital assistant (PDA): A personal organisation device that includes schedule planners, address books, to-do lists, memos, e-mail and faxes software. Some advance models even allow the user to surf the Internet. PDAs have a small screen that acts as both an input and output device. On the screen, you can display your appointments for the day, and you can also use a special writing stylus to capture information. The screen is touch sensitive, allowing you to write directly on the screen with the screen capturing what you are writing.
2. Types of memories

On the motherboard are memory chips, of which there are 4 types: RAM, ROM, CMOS, and flash.

1. RAM (for random access memory) chips temporarily hold software instructions and also data before and after processing by the CPU. RAM is volatile; i.e. its contents are lost when the power goes off. Three types of RAM chips are DRAM (dynamic RAM), which must be constantly refreshed by the CPU or it will lose its contents; SDRAM (synchronous DRAM), which is faster than DRAM; and SRAM (static RAM), also faster than DRAM and able to retain its contents without being refreshed by the CPU. RAM chips often appear on memory modules – SIMM (single inline memory module) has chips on one side; DIMM (dual inline memory module) has chips on both sides – which can be plugged into expansion slots on the motherboard.
2. ROM (for read-only memory) chips contain fixed start-up instructions. (Read means to transfer data from an input source to the CPU or memory; write means to transfer data from the CPU or memory to an output device.) A variant is PROM (programmable ROM), a ROM chip that allows users to load read-only programs and data, although only once.