There is a computer for every use under heaven, or so it seems. Let's look at the kinds of computers that there are, based on general performance levels.

Personal or micro

Computers for personal use come in all shapes and sizes, from tiny PDAs (personal digital assistant) to hefty PC (personal computer) towers. More specialized models are announced each week - trip planners, expense account pads, language translators...
hand-held computer
Hand-held (HPC)
personal digital assistant


Tablet PC
laptop computer
Desktop computer

When talking about PC computers, most people probably think of the desktop type, which are designed to sit on your desk. (Bet you figured that one out!) The tower and the smaller mini-tower style cases have become popular as people started needing more room for extra drives inside. Repairmen certainly appreciate the roominess inside for all the cables and circuit boards ... and their knuckles.

A workstation is part of a computer network and generally would be expected to have more than a regular desktop PC of most everything, like memory, storage space, and speed.

The market for the smallest PCs is expanding rapidly. Software is becoming available for the small types of PC like the palmtop (PPC) and handheld (HPC). This new software is based on new operating systems like Windows CE (for Consumer Electronics). You may find simplified versions of the major applications you use. One big advantage for the newer programs is the ability to link the small computers to your home or work computer and coordinate the data. So you can carry a tiny computer like a PalmPilot around to enter new phone numbers and appointments and those great ideas you just had. Then later you can move this information to your main computer.

With a Tablet PC you use an electronic stylus to write on the screen, just like with a pen and paper, only your words are in digital ink. The Tablet PC saves your work just like your wrote it (as a picture), or you can let the Hand Recognition (HR) software turn your chicken-scratches into regular text.

Main frame

The main frame is the workhorse of the business world. A main frame is the heart of a network of computers or terminals which allows hundreds of people to work at the same time on the same data. It requires a special environment - cold and dry. Main Frame computer


The supercomputer is the top of the heap in power and expense. These are used for jobs that take massive amounts of calculating, like weather forecasting, engineering design and testing, serious decryption, economic forecasting, etc.
A Gallery of images of Cray supercomputers - from the current model back to the earliest.

The first Cray supercomputer was introduced in 1976 - the Cray-1.

Distributed or Grid Computing

The power needed for some calculations is more than even a single supercomputer can manage. In distributed computing using a PC grid many computers of all sizes can work on parts of the problem and their results are pooled. A number of current projects rely on volunteers with computers connected to the Internet. The computers do the work when they are not busy otherwise. 

The projects that need distributed computing are highly technical. For example, the http://setiathome.ssl.berkeley.edu/ project looks for signs of intelligent communication in radio signals coming from space. (SETI stands for Search for Extra-Terrestrial Intelligence.) 

If you volunteer your computer for this project, you might be asked to load a small screen-saver program onto your own computer. When the computer is not busy, the screen saver comes on. The program downloads some signal data, starts to analyze it, and later reports the results back to SETI@Home.  Once the program is installed, you do not have to do anything else but watch the progress in the screen saver. 

Another method does not use a screen saver, but uses any idle time on your computer to work on the project. Results are sent to the project's home over the Internet.

Some current distributed computing efforts are: 

modeling evolution of resistance to drugs and designing better AIDS treatments
http://folding.stanford.edu/ working on how proteins fold, which is important to understanding how they work and reproduce
Distributed.Net cryptography and mathematical problems
http://demo.cs.brandeis.edu/golem/  (Genetically Organized Lifelike Electro Mechanics) evolving robots
PiHex  calculating the value of Pi to certain large places (done!)

Other Important Terms


The term server actually refers to a computer's function rather than to a specific kind of computer. A server runs a network of computers. It handles the sharing of equipment like printers and the communication between computers on the network. For such tasks a computer would need to be somewhat more capable than a desktop computer. It would need:

more power

server computer

larger memory

larger storage capacity

high speed communications


The minicomputer has become less important since the PC has gotten so powerful on its own. In fact, the ordinary new PC is much more powerful than minicomputers used to be. Originally this size was developed to handle specific tasks, like engineering and CAD calculations, that tended to tie up the main frame.

For more on the history of computing:  The Computer Museum History Center  The center traces the development of the computer. The site includes a timeline that is sorted by year or by topic. You can also search for information on people, companies, and products in the computer industry.

Now you are ready to proceed to the next lesson.