Executive Statement A mainframe is a very large, powerful, dedicated, multi-tasking computer where enormous amounts of data are processed, sometimes millions of records a day. The mainframe is set up for specific applications and those applications only; which is totally different from a Personal Computer (PC). A mainframe runs a custom operating system specifically written for particular applications while a PC has a generic operating system such as Windows and is built to handle many different programs. PC's are multi-tasking but not dedicated with control of the resources usually handled by the computer rather than the user having control over the amount of resources used by any given application.

For example, if you were to run 3 D Studio Max, it would use 100% of your processor and about 75% of your Random Access Memory (RAM) to render a scene but if you were working with a similar mainframe program you would be able to use the assigned 'chunk' of the processing power for rendering and that would still leave the dedicated amount for other applications or users to use (L. Mitzner, personal communication, January 12, 2002). PC's and Mainframes Defined In comparing and contrasting PC's and Mainframes it is necessary to first understand what a PC and a Mainframe are. Because IBM produced the first personal computer, the term PC came to mean IBM or IBM-compatible personal computers, which excluded other types of personal computers such as Macintosh es, though I rarely hear the term IBM-compatible used anymore when referring to the term PC. Put quite simply a mainframe is a very large computer that is totally different from a PC. Some of the differences between mainframes and PC's are size, power, ability to dedicate resources, and the amount of data that can be processed.

The mainframe is set up for specific applications and those applications only; that is totally different from a PC. For example, you couldn't load Word or Internet Explorer onto a mainframe computer. It is true that, as to processing power, what was a mainframe yesterday is on desktops today, but that is where the similarities end. The Central Processing Unit (CPU) is the brains of the computer where most of the calculations take place and it is the most important element of a computer system. For the PC the CPU is housed in a chip (known as the microprocessor) such as the Intel Pentium chip. On a Mainframe computer CPUs require one or more printed circuit boards (PC board).

Mainframe is the name that was given to this machine by the industry that came from the way they built the machine by first putting up a metal frame and then installing all of the components or units, such as the processing unit and the communication unit, into this frame hence the term: Mainframe. PC's and Mainframes Explained Personal computers, otherwise known as Microcomputers, are everywhere, on our desks, at home and at work, on tables, in offices, thus making them the most visible form of computers in the world today. Even though they come from many different makers, in different sizes, shapes and colors, the design and technical specifications used for PC's has remained constant for generations. A personal computer is a stand-alone machine with most of the computing done physically on the computer itself. When networking started to integrate into offices PC'S became connected with network servers, and mainframes. For applications and large-scale computing purposes of very large corporations, businesses, government, banking and educational institutions, a large company, such as IBM, typically manufactures a mainframe.

Historically, a mainframe is associated with centralized computing. Today, IBM refers to larger processors and servers and they emphasize that they can be used to serve distributed users and smaller servers in a computing network. What do they look like? A personal computer can be housed in a mini-tower; a mid-tower or a full-tower or it can be the flat desktop housing that has the monitor sitting on top of it. Several years ago, I worked for the IRS and they had a computer room. This room was very large, kept refrigerated and housed several mainframes.

These machines were typically 8-9 feet tall, about 3 feet or more wide and they were made of grey colored steel. They had lots of lights and dials and such. The data storage was reel-to-reel tape onto which data was downloaded twice a day. So how Big is Big? The main purpose of a mainframe was to run commercial applications and large-scale computing, such as that done by the IRS, and banks where enormous amounts of data are processed sometimes millions of records a day.

A typical mainframe has the following characteristics: . A mainframe has several CPUs... Memory is hundreds of Gigabytes of RAM and It has tons of hard drive storage... Its processing power is over 550 Mips... It often has different cabinets for storage, input / ou put and RAM...

Distributes the workload over different processors and input / output devices. It can handle a large number of users... All processes are running on the host and not on the terminal... Output is sent to the terminal through a program running (in the background) on the mainframe. In my case it is called PIMS... Nothing else goes over the line Management processes, such as program management and task management, are separate.

A mainframe is usually associated with centralized computing where all computing physically takes place on the mainframe itself (L. Mitzner, personal communication, January 12, 2002). Operating Systems In the beginning most mainframes were hard wired so there were no operating systems for them. Programming involved rewiring panels and re-setting loads of switches (L. Mitzner, personal communication, January 12, 2002). With the advent of more memory and the availability of programming languages programmers created the sophisticated operating systems that were needed by mainframes.

The Operating system for a mainframe is very different than the one written for the desktop PC and there are very few mainframe operating systems. Remember the desktop PC usually has only one (sometimes 2) CPUs and a limited amount of random access memory (approximately 1 gigabyte maximum) that it can handle. The mainframe has several CPU boards and more than 8 gigabytes of memory. The operating system for the mainframe where I work, and the mainframe I worked on at the IRS, was text based as many of them are, and they can be connected to personal computers with a special interface program called groupware that allows the LAN/WAN, Mainframe, and Internet to be accessed via the groupware on workstation PC's. Conclusion A mainframe is a very large machine that has several processors, large amounts of memory and hundreds of gigabytes of RAM. It has masses of disk space and other storage facilities in large size and quantities that are not normally found with Personal computers.

The actual difference comes in the scale and power of the mainframe machine and it's ability to process large amounts of data at amazing speeds, whereas the PC is limited in size and scope as to its abilities processing small amounts of data with a limited amount of power. For large business, the main frame is a necessary but for most home computing a PC is everything they need.