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Computers : The heavyweights and the featherweights

Generally, when someone mentions the word, 'computer', the image that many of us visualise in an instant, is the personal computer which basically comprises the monitor, system unit, keyboard and mouse.

But, in fact, computers are classified into a few basic categories depending on their size and computational capacity and power, and each has its own significance. Let's check out these categories, namely, Supercomputers, Mainframe Computers, Minicomputers and Microcomputers and see how they fare in the computer arena.

Mainframe Computers

These too are heavyweights in the family of computers. In contrast to Supercomputers, the key feature of Mainframes is that they are mainly focused on bulk data processing which involves a lot of input/output activities.

A census is such an instance. Mainframes generally have the ability to run for several years even without a major breakdown, and there is a high fault tolerance since a lot of input/output activities take place.

During the 1960s, basically punch card inputs and printed outputs were used, where the operations were done in batches. In the 1970s, interactive user interfaces were used, and this enabled many users to interact with the mainframe through different terminals in a timesharing manner which are known as 'dumb terminals', meaning that they cannot independently do any processing without the help of the mainframe.

Graphical user interfaces came into existence in the 1980s.Almost all mainframes can have multiple operating systems which operate as a series of virtual machines which becomes a better option in replacing many servers.

Millions of instructions per second (MIPS) has been the yardstick used to measure the CPU speeds of mainframes. But now, other criteria such as CPU power, I/O capacity and virtualisation capabilities are taken into account.

The many processors in a mainframe handle certain services, helping the main processor. But in supercomputers, there are generally no service processors. The main focus is on speeding up the computational abilities of the relevant processors.

Supercomputers

These lead the computer world as the top performers when it comes to computational capabilities. These are used in instances where heavy calculations are necessary such as quantum mechanical physics, whether forecasting, physical simulations, and nuclear energy research etc.

Have you ever heard of 'Grand Challenge' problems? Well, these are problems which need immense computing resources to arrive at a solution, and supercomputers are the preferred options when it comes to tackling such specific issues.

The intense operations generate a lot of heat in these, and special cooling systems are required. Measures should be taken to enable a fast information transfer between components, and one step taken by Cray Supercomputers is making cylindrical supercomputers which reduced the length of data paths.

Minicomputers

Minicomputers can be defined as computers which fall between mainframes and small single user systems, or in other words, microcomputers. These have most of the features of a mainframe, but, in a limited scale.

They can have many terminals as in mainframes, but the number is far less than the number possible with mainframes. These are preferred for medium scale businesses.

Minicomputers originated as a result of the miniaturisation of computers which took place after the invention of the transistor and the IC.

The first minicomputer launched in 1964 was known as the PDP-8. However, as technology evolved, further integration caused microcomputers to be more powerful and minicomputers became physically more like microcomputers.

As networking became popular, the dumb terminals were replaced by PCs which could process data independently. As a result, usage of minicomputers became limited, but still they are in operation as servers.

Microcomputers

These are the kids in the computer family, and they are generally characterised by their limited space usage and the usage of a single microprocessor. In fact, the microprocessor which originated as the many components of a minicomputer's CPU were housed in a single chip.

Anything smaller than servers, which can be Personal Computers, laptops, tablet PCs, PDAs, and handheld devices fall in to this category. Most microcomputers serve only a single user at a time.

However, some can serve in the form of PCs and workstations while serving several users concurrently. Basically, a microcomputer is made up of a microprocessor, a volatile primary memory, a comparatively larger secondary memory such as a hard disk, and some other devices such as I/O devices, human interface devices etc.