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Supercomputers

Supercomputers are very large computers with very large computing power and huge RAM.  What distinguishes a supercomputer from the others is the use of massively parallel processing.  For example, one supercomputer contains 5800 processors and more than a trillion bytes of RAM.  Rather than taking a program and executing it sequentially, a supercomputer takes the program, divides it and each part of the program is then executed concurrently on different processors.  (Of course, programs have to be specially designed to take advantage of the supercomputer architecture.

Supercomputers are mainly used in the sciences an engineering, though defense intelligence agencies also use them.  For example, weather forecasting involves the modelling of current weather patterns and predicting future patterns.  This use of super computers requires a very large number of computations and large amounts of data -- ideal for supercomputers.

The number of users of a supercomputer is usually in the range of dozens of people.

An example of a supercomputer is the Cray, above.

Mainframe Computers

Banks, insurance companies and large national or international companies use mainframe computers.  A mainframe may be shared by large number of users, often numbering in the hundreds. Processing, storage and printing are shared services provided on a mainframe.

Processing Modes

Programs that require the continued participation of a user are interactive -- the user interacts with the computer through its user interface.  Most mainframes use command line or menu-driven interfaces.

On the other hand, many tasks (like sending out hundreds of thousands of Visa or MasterCard bills) can be performed by the computer without the active participation of a user.  A user or computer operator submits a job to the computer, the computer does the work, and the computer displays a message when the program is completed.  These programs may run for many hours and are called batch programs -- transactions (e.g. printing bills) are "batched" and run at one time in a large "batch".

Common hardware for mainframe computers includes the IBM 390 family of computers, running the OS390 operating system.  Users often interact with the system through TSO (a command line interface) or ISPF (a menu-driven productivity interface).  Batch programs use JCL (a special job control language) which specifies the program(s) to be run, the data set(s) and the devices to be used.

Mainframe computers often require a group of specialist computer operators to run the organization's systems and programs.

Mini-computers

A mini-computer is larger than a PC but generally smaller than a mainframe.  A common operating system is UNIX though manufacturers may have their own proprietary operating systems as well.  An example is the IBM AS/400 (using the OS/400 operating system) which has a command line / menu-driven interface.  A mini-computer, depending on size (which varies greatly), may have from a dozen to perhaps a few hundred users.  Mini-computers are well suited for use in commercial, business, engineering and scientific applications.

Because mini-computers often run "unattended", the term "lights-out operations" is often applied to mini-computer operations -- no need to turn on the lights because there are no people in the room!

Networks

Computer networks offer departments and small groups an opportunity to share printers, centralized file storage (on a file server) and other services.  Common network operating systems are Windows 2000 Professional Workstation (at the user end) and Windows Professional 2000 Server (at the server); Novell (a competing product of similar capabilities); and, LINUX (a PC-based version of UNIX) which is very fast and reliable as a server.  Often, there is quite a tangle of wires behind a server!

Stand-alone PC

The PC itself has many very important and advanced capabilities.  Users may perform many work place tasks such as writing documents, performing calculations, accounting, or other tasks.  (Just think about your personal use of PCs!)

Do a search on the internet to find out more.  A good idea is to search the words or phrases that are in blue italics above.