Types of Mainframe Computers
By Shea Laverty
Mainframe computers are large-scale systems designed for processing and storing huge amounts of data that smaller systems such as PCs can't handle. They are frequently used by extremely large companies, banks and government agencies that have enormous processing and storing needs, and can handle hundreds of users at the same time. Named for the framework on which the computers used to be hung, mainframes are also known as "big iron" and have continued to adapt and evolve beyond their original limitations to keep pace with technological advancement.
Size
A mainframe computer's size depends primarily on its age. Most mainframes produced before 2000 are sprawling leviathans, consisting of upwards of 10,000 square feet of rack-hung computers spanning one or more floors in a company's offices or off-site facility. With the miniaturization of computing elements, the modern mainframe is considerably smaller -- often approximately the size of a large refrigerator. Depending on the scale of the mainframe, the needs of the company and the associated costs, mainframes can see many years of service before they're unable to handle the workload.
Purpose
Mainframe computers were designed to handle large-scale processing, data storage and other tasks too resource-intensive for the average computer or small-scale network to handle -- for example, a bank's transactions. The exact processes handled tend to vary based on the users, but mainframes generally shift huge amounts of data that would tax smaller systems beyond the breaking point -- and they do it quickly and reliably in order to facilitate the needs of users on an enterprise scale.
Primary Manufacturers
Because of the prohibitive cost of development and deployment, only a handful of manufacturers make and develop mainframes. Primary producers of mainframe equipment and software include IBM, Hewlett-Packard, Unisys, Fujitsu, Hitachi and NEC. These manufacturers supply mainframe equipment to clients around the world, to clients in both the public and private sectors. Mainframes are an extremely costly investment -- in 2012, IBM released a "lower-price" mainframe system starting at $75,000. Typically, mainframes cost even more, with prices varying based on equipment-type purchased and the scale of the mainframe.
Terminals
Mainframe computers are primarily accessed and controlled via terminals -- computer workstations that superficially resemble standard computers but typically have no CPU of their own. Instead, they are networked to the mainframe and act as an access point for users.
Operating Systems
The operating system installed on a mainframe varies depending on the manufacturer. Most mainframes use Unix, Linux variants or versions of IBM's zOS operating system. These operating systems are often configured specifically for the mainframe on which they run and offer users any necessary interface capabilities.
Centralized vs. Distributed Computing
Traditional mainframe computers use a "centralized" computing scheme -- the mainframe is an insular system in which only directly connected terminals are capable of accessing information. As Internet communication and operation has gained prevalence, centralized mainframes have become increasingly more open towards a "distributed" computing scheme. Distributed mainframes can be accessed by computers outside of the mainframe itself, allowing users to access material from their homes or on the go via the Internet.
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