PC: Abbreviation for "Personal Computer," 93% of the computer population uses PCs. PCs for personal use come in almost any shape and design, they usually run Microsoft Windows (for example, Windows XP, Vista, or Windows 7), are exceptionally fast, and are compatible with almost all available computer applications. Most large-scale businesses, corporations, schools, and home users operate PCs due to their customizable features, performance, and generally low price. Leading PC manufacturers include Dell, HP, Samsung, Sony, Toshiba, and many others.
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It should be mentioned that when people refer to a PC in general conversation, they are (almost always) referring to a Microsoft Windows compatible personal computer. These computers are not limited to running the Windows family of operating systems, but their architecture is compatible with the requirements of claiming compatibility. Historically, these would have been explained as "IBM PC" or "IBM Clone" computers.
PC's in general can function as servers or workstations, depending on their implementation. These may be graded, or configured as:
Personal use - Most commonly thought of as a "PC"
Business Class Workstation - the "PC" qualification starts getting a little grey here.
Business Class Server - no longer considered a "PC"
Laptop: A compact, battery powered version of a PC. Also called a "Notebook."
Macs: Even though the Mac (short for "Macintosh") is a form of personal computer, it is different from a PC because it does not use Microsoft Windows as the Operating System. Instead, it uses the Mac OS series, such as OS X Leopard.
Macs are known for their incredible system stability, quality designs, unique programs and features, and their usually fast speed. Macs are becoming more popular in society, generally used in peoples' homes or in digital graphic design studios. Unfortunately, many people do not invest their money in a Mac because of a Mac's steep price (a $1500 Dell PC is about the same price of a $2400 Apple Macktintosh--both with the same specifications) and the lack of many compatible programs made specifically for Macs (although the number is increasing).
Mainframe : Computers with large Hard Drives, lots of Memory (RAM), multiple CPUs running together, which perform large amounts of computing depending upon the speed of the processors used and amount of RAM included.
Micro Computer : A very small computer, usually used in cameras.
Super Computer : A computer with lots of processors, Memory (RAM), etc. Usually used in scientific research work or they are used by the government. For large manufacturers, a supercomputer typically "breaks down" problems, solves them in small "bits," and then puts the problem "back together." They have a capability of 14,000 micro computers.
PDA: "Personal Digital Assistant" or Palmtop.
Analog : Older, out-dated computers. They calculate physical Quantities such as voltage, etc...
Digital: Computers which use binary digits (zeros and ones) for processing. Almost all electronic computing devices are digital, including PCs, Macs, and Servers.
Server: A computer with great processing power that receives and performs requests from other computers.
What the above answers are stating are names/applications/types of electronic computers. Electronic computers can be subdivided into analog or digital. At a basic level, all digital electronic computers are composed of several parts - including input/output (LCDs, LEDs, keypads, printers, etc.), a processor (often includes an arithmetic logic unit, controller, registers, etc., but doesn't necessarily need to contain all of these), and memory. Analog computers were the predecessors of these digital computers, and are still used in some applications today.
A "computer" is simply something used for performing calculations. A "long" time ago (World War 2), Computer was a title/job description, literally meaning someone who did computations. This definition would also stretch computer to cover mechanical devices, such as the enigma machines used in WW2 for ciphers (by the Germans).
A: Names application random subjects of references but it still boils down to a three components. A German machine did not do computations but rather simplify the process of elimination.
