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Essay on PCs versus Mainframes
Computers are categorized into Microcomputers, Minicomputers and Workstations, Mainframes, Supercomputers. The Microcomputers like PC, Apple Mac Originated in late 70's were Single-user-oriented, the Minicomputers and Workstations are smaller versions of mainframe, usually run on either the highly portable Unix Operating System or close Operating System. The Mainframes are oldest form of computers, Expensive and powerful, Small, Medium, and Large-Program handling Uniprocessor, high-speed storage can be shared by a wide variety of users.
Mainframes can handle large volumes of data and Provide centralized administration Offer superior data management capabilities, can handle different types of workload, have high data bandwidth, Monitor data integrity and security. Mainframes use Operating Systems which have functions like System Management, Resources Management, Memory Management, and File Management. The characteristics of Mainframe Operating System are Virtual storage, Multi-programming, Spooling, Batch processing.
Four nines availability” and “Five nines availability” are terms unfortunately unfamiliar to PC users. Yet it is these figures 99.99% and 99.999% availability that are used to rate the reliability of mainframes. Such figures equate to between 5 and 53 minutes of downtime a year. In fact, for System/390 mainframes the average time between failures that force a reboot and an initial program load is 20 to 30 years. Such reliability is truly stunning from the perspective of a PC user, yet this kind of performance is crucial to businesses where a crash could incur losses of millions of dollars for every hour of downtime.
A fundamental difference between mainframes and PCs is the respective attitudes shown towards them. If a PC crashes, it's a problem. Work is lost, the user is unhappy, but then reboots the system and redoes whatever was lost. It's unlikely the system administrator would even hear about it. If however, a mainframe crashes, it's a major catastrophe.
The advent of minicomputers in the seventies and desktop PCs in the eighties was expected to ring the death knell for mainframes, which were considered to be large, inflexible, expensive and difficult to use....
