Mainframe Operating Systems

Beginners Guide to How Operating Systems Work
Beginners Guide to How Operating Systems Work

Mainframe computers are very large computers that are built to be able to perform complex and critical applications. They are usually very large in both physical size and computational ability, and they can be some of the largest machines on the planet. However, given the continued drive toward greater computational muscle in a smaller physical package, many mainframes are not too much larger than desktop computers these days.

A pair of IBM mainframes. On the left is the IBM z Systems z13. On the right is the IBM LinuxONE Rockhopper.
A pair of IBM mainframes. On the left is the IBM z Systems z13. On the right is the IBM LinuxONE Rockhopper.

These large computers are designed to keep running with as little interruption as possible. They contain large numbers of self-maintenance features, including built-in security features and backup power supplies. Since mainframes are usually the most important computers in a company’s computational arsenal, they are routinely protected by multiple layers of security and power backup, both internal and external.

Among the self-protection measures commonly found in mainframes are an enhanced heat-protection mechanism. Since these computers run all day every day for years at a time, they naturally build up a large amount of heat that needs to be vented. The fans found in mainframes are some of the most effective in the business.

Because mainframes are at the top of the network system food chain, they routinely have the best and most up-to-date of everything, including processors, hard drives, video cards, network cards, and peripheral connections. With such a computer, which is designed to be super-fast, super-sleek, and super-powerful, read and write speeds have to be lightning-quick. Many have multiple processors as a result.

One of the most important functions of a mainframe is to be able to host applications and work with multiple users simultaneously. Not all computers can handle this, so mainframes are very important in a company’s electronic design, especially its network design. Very often, they are at the heart of computer networks.

In today’s on-demand, Web-driven world, mainframes are playing an even more central role in providing — and controlling — access to and from networks. The number of users that can access this computer at one time is seemingly limitless. Mainframes in this environment are also designed to host Web-based applications.

Mainframes typically can run more than one operating system at a time as well. This comes in handy when a company is running a Web-based system whose users include practitioners of Mac OS, Linux, and Windows XP. It allows a company to avoid having to exclude users because of OS issues.

Larger mainframes are not always user-friendly, unless the user is the system administrator. These computers are designed to stay running, not to be available for users’ whims. However, the lack of approach-ability is more than made up for by their increased ability to keep running in situations that would likely disable other systems.

Early mainframe computer programs were contained in stacks of cardboard punch cards. Although it has been many years since they have been used for this purpose, punch cards still have a few uses, and are most notably used in some voting machines.

Punch cards were actually invented before electronic computers. Originally patented by Herman Hollerith, the punch card was first used with tabulating machines to record vital statistics by the New York City Board of Health, and later, in the 1890 census. Hollerith actually got the idea from the cards used in Jacquard looms, which use cards to control a weave pattern.

Hollerith invented electromechanical machines that included a punch device, a tabulating machine and a sorting machine, which could be used to accumulate and store statistics. His company, the Tabulating Machine Company, was later joined by Thomas Watson, who later renamed the company International Business Machines (IBM).

The size and number of columns has varied over the years, with the original card used in the 1890 census having 20 columns with 10 punch positions each. There are a few interesting parallels to modern operating systems. In 1928, IBM introduced and patented the 80 column card that used rectangular holes instead of round holes, which was significant because it limited IBM’s competitors to the older, incompatible round-hole format.

Remington Rand designed a competing format that permitted 90 columns of text to be stored on 45 column cards, which was actually a superior design, but because of IBM’s dominance of the market, were not used as often. Card processing did not necessarily require the use of a computer. Some retail applications, for example, used a card sorter and tabulating machine for accounting functions, such as totalling price fields on cards in multiple categories.

Programming languages required the early fixed format cards to move to a free format design, and with the development of standardized computer languages such as FORTRAN and COBOL, generic punched cards became prevalent.

It wasn’t until the 1970s that large data processing operations began shifting from punch cards to timesharing environments with data stored on magnetic tape.

Punch cards are still widely used in voting machines, despite problems that have occurred over the years. In the 1968 general election in Detroit, a rainstorm soaked one batch of ballots, and in the 2000 presidential election, questions arose as to their accuracy and efficiency as compared to more modern systems.

About Mike Casimir 147 Articles
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