A computer is a programmable machine. It accepts information in the form of digitalized data and manipulates it for some result based on a program or sequence of instructions on how the data is to be processed.
It consists of at least one processing element, typically a central processing unit (CPU) and some form of memory. The processing element carries out arithmetic and logic operations, and a sequencing and control unit that can change the order of operations based on stored information.
The first use of the word “computer” was recorded in 1613 in a book called “The young man’s gleanings” by English writer Richard Braithwaite” I have read the truest computer of Times, and the best Arithmetician that ever breathed, and he reduced thy days into a short number.” It referred to a person who carried out calculations, or computations, and the word continued with the same meaning until the middle of the 20th century. From the end of the 19th century the word began to take on its more familiar meaning, a machine that carries out computations.
Computers are also categorized on the basis of physical structures and the purpose of their use. Based on Capacity, speed and reliability they can be divided into four categories of computers:
- Microcomputer: A small, single-user computer based on a microprocessor.
- Minicomputer: A multi-user computer capable of supporting up to hundreds of users simultaneously.
- Mainframe: A powerful multi-user computer capable of supporting many hundreds or thousands of users simultaneously.
- Supercomputer: An extremely fast computer that can perform hundreds of millions of instructions per second.
A microcomputer is a small, relatively inexpensive computer with a microprocessor as its central processing unit (CPU). It includes a microprocessor, memory, and input/output (I/O) facilities. Microcomputers became popular in the 1970s and 80s with the advent of increasingly powerful microprocessors.
Microcomputer or personal computer can be defined as a small, relatively inexpensive computer designed for an individual user. Businesses use microcomputers for word processing, accounting, desktop publishing, and for running spread sheet and database management applications. At home, the most popular use for microcomputers is for playing games and recently for surfing the Internet.
The characteristics of a microcomputer are Monitors, keyboards and other devices for input and output may be integrated or separate. Computer memory in the form of RAM, and at least one other less volatile, memory storage device are usually combined with the CPU on a system bus in one unit. Other devices that make up a complete microcomputer system include batteries, a power supply unit, a keyboard and various input/output devices used to convey information to and from a human operator (printers, monitors, human interface devices). Microcomputers are designed to serve only one user at a time, although they can often be modified with software or hardware to concurrently serve more than one user. Microcomputers fit well on or under desks or tables, so that they are within easy access of users. Bigger computers like minicomputers, mainframes, and supercomputers take up large cabinets or even dedicated rooms.
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Actual microcomputer can be generally classified by size and chassis / case. The chassis or case is the metal frame that serves as the structural support for electronic components. Every computer system requires at least one chassis to house the circuit boards and wiring. The chassis also contains slots for expansion boards. If you want to insert more boards than there are slots, you will need an expansion chassis, which provides additional slots. There are two basic flavours of chassis designs-desktop models and tower models-but there are many variations on these two basic types. Then come the portable computers that are computers small enough to carry. Portable computers include notebook and subnotebook computers, hand-held computers, palmtops, and PDAs.
The term refers to a computer in which the power supply, motherboard, and mass storage devices are stacked on top of each other in a cabinet. This is in contrast to desktop models, in which these components are housed in a more compact box. The main advantage of tower models is that there are fewer space constraints, which makes installation of additional storage devices easier.
A computer designed to fit comfortably on top of a desk, typically with the monitor sitting on top of the computer. Desktop model computers are broad and low, whereas tower model computers are narrow and tall. Because of their shape, desktop model computers are generally limited to three internal mass storage devices. Desktop models designed to be very small are sometimes referred to as slim line models.
Notebook is extremely lightweight personal computer. Notebook computers typically weigh less than 6 pounds and are small enough to fit easily in a briefcase. Aside from size, the principal difference between a notebook computer and a personal computer is the display screen. Notebook computers use a variety of techniques, known as flat-panel technologies, to produce a lightweight and non-bulky display screen. The quality of notebook display screens varies considerably. In terms of computing power, modern notebook computers are nearly equivalent to personal computers. They have the same CPUs, memory capacity, and disk drives. However, all this power in a small package is expensive. Notebook computers cost about twice as much as equivalent regular-sized computers. Notebook computers come with battery packs that enable you to run them without plugging them in. However, the batteries need to be recharged every few hours.
A small, portable computer small enough that it can sit on your lap. Nowadays, laptop computers are more frequently called notebook computers.
A portable computer that is slightly lighter and smaller than a full-sized notebook computer. Typically, subnotebook computers have a smaller keyboard and screen, but are otherwise equivalent to notebook computers.
A portable computer that is small enough to be held in one’s hand. Although extremely convenient to carry, handheld computers have not replaced notebook computers because of their small keyboards and screens. The most popular hand-held computers are those that are specifically designed to provide PIM (personal information manager) functions, such as a calendar and address book. Some manufacturers are trying to solve the small keyboard problem by replacing the keyboard with an electronic pen. However, these pen-based devices rely on handwriting recognition technologies, which are still in their infancy. Hand-held computers are also called PDAs, palmtops and pocket computers.
Palmtop is small computer that literally fits in your palm. Compared to full-size computers, palmtops are severely limited, but they are practical for certain functions such as phone books and calendars. Palmtops that use a pen rather than a keyboard for input are often called hand-held computers or PDAs. Because of their small size, most palmtop computers do not include disk drives. However, many contain PCMCIA slots in which you can insert disk drives, modems, memory, and other devices. Palmtops are also called PDAs, hand-held computers and pocket computers.
PDA is short for personal digital assistant, a handheld device that combines computing, telephone/fax, and networking features. A typical PDA can function as a cellular phone, fax sender, and personal organizer. Unlike portable computers, most PDAs are pen-based, using a stylus rather than a keyboard for input. This means that they also incorporate handwriting recognition features. Some PDAs can also react to voice input by using voice recognition technologies. The field of PDA was pioneered by Apple Computer, which introduced the Newton Message Pad in 1993. Shortly thereafter, several other manufacturers offered similar products. To date, PDAs have had only modest success in the marketplace, due to their high price tags and limited applications. However, many experts believe that PDAs will eventually become common gadgets.
PDAs are also called palmtops, hand-held computers and pocket computers.
Another type of computer is Micro Computer which is design to support more than one user at a time but it can be used by one person at a time. It is a computer of a size intermediate between a microcomputer and a mainframe computer and includes a microprocessor, memory, input and output facility and it comes equipped with at least one type of data storage, usually RAM. Typically, mini computers have been stand-alone computers sold to small and mid-size businesses for general business applications and to large enterprises for department-level operations. . Mini computers were designed for control, instrumentation, human interaction, and communication switching as distinct from calculation and record keeping. They have great storage capacity and work at a high speed rate. It is often use in place where several people have to work at the same time, so it let many users use data at the same time without any inconvenient. Mini computers are not only used in organization for work but many of mini computers are also used as personal computer. It has a large cheap array of silicon logic gate which allows utility programs and self-booting kernel to be stored within microcomputers. These stored programs let the minicomputer to automatically load further more complex software from external storage device without the user intervention.
The Minicomputers were first built in in 1960s and they immediately became a huge success as 40,000 of the minicomputer systems were immediately sold of making the computers hugely available to the general public. With such a successful market possibility many companies stepped in to venture in the minicomputer market. The most successful among these two hundred companies was DEC that launched the minicomputer models PDP-11 and VAX 11/780.
Some significant characteristics and historical facts about the mini computer system have been summarized as follows:
They are much smaller in size than the mainframe computer systems. As such they do not occupy an entire room but usually occupy space similar in size to that of a standard refrigerator.
They are much less expensive than the mainframes.
Their invention was possible because of the invention of core memory technologies and transistors.
Minicomputers can give parallel access to up to 100 users. Hence they were used in places such as business organizations for maintaining billings and finances.
Some of the very first companies to manufacture the minicomputer systems were Hewlett Packard, DEC and Data General.
A few models of minicomputers which have been a marked success over the years are:
DEC VAX series and PDP series
Hewlett Packard HP3000 series
Prime Computers, Prime 50 Series
Norsk Data, Nord-1, Nord-10, Nord-100
IBM Midrange Computers
Control Data Corporation’s CDC 160A, CDC-1700
Data General Nova
Honeywell-Bull Level 6/DPS Level6/DPS 6000 series
Minicomputers have eventually evolved in to microcomputers. With the launch of microcomputers, the public have
Had a greater access to the advantage of incorporating computers in the daily stride of their lives.
4. MAINFRAME COMPUTER
In another hand we have the Mainframe Computer which is quite expensive than the Mini computer. In comparison the mainframe computer perform better than the mini computer, it can process data at a very high speed rate, for example, millions of instruction per second and Compared to a typical PC, mainframes commonly have hundreds to thousands of times as much data storage online, and can access it much faster. They contain a large number of self-maintenance features, including built-in security features and high data handling capacity. Because of mainframe’s ability to handle high level data transactions they are used by the biggest firms in almost all the industry such as banks, government agencies and organizations which need to store great volume of complex and important data at a high security level, which means that this is the most secure than other type of computer.
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Mainframes are designed to handle very high volume input and output and emphasize throughput computing. This type of computer can work for long period without being interrupted, they are reliable. It can run multiple different instance of different operating system and can handle the work of many users at the same time. The term RAS (reliability, availability and serviceability) is a defining characteristic of the mainframe computer. Test, development, training, and production workload for applications and databases can run on a single machine, except for extremely large demands where the capacity of one machine might be limiting. They are usually protected by multiple levels of security and power backup, both internal and external. Among the self-protection measures commonly found in mainframes are an enhanced heat-protection mechanism. Because these computers run all day along with 24x7x365 ability, a large amount of heat generated must be expelled. The fans in mainframe computers are among the most efficient helping in keeping the data centers cool.
They are huge computers installed in space centers, nuclear power stations etc. They are used for performing complex mathematical calculations. Only scientists and mathematicians can operate them. They are having huge memories & tremendous processing speed. They are used for weather forecasting, animation graphics…
Mainframes run multiple sessions, and with high reliability. Companies can run their IT operations for years without problems or interruptions with minimum down time. Administration is very easy due to the fact that all applications layers are monitored in one Server.
A central computer alone can replace dozens or hundreds of smaller PCs, reducing management and administrative costs while providing a much better scalability and reliability.
Mainframes can run more than one operating system at once, which allows companies to run multiple sessions with a super-fast speed, high reliability, and high secure.
Supercomputer is a broad term for one of the fastest computers currently available. Supercomputers are very expensive and are employed for specialized applications that require immense amounts of mathematical calculations (number crunching). For example, weather forecasting requires a supercomputer. Other uses of supercomputers scientific simulations, (animated) graphics, fluid dynamic calculations, nuclear energy research, electronic design, and analysis of geological data (e.g. in petrochemical prospecting). Perhaps the best known supercomputer manufacturer is Cray Research.
Approaches to supercomputer architecture have taken dramatic turns since the earliest systems were introduced in the 1960s. Early supercomputer architectures pioneered by Seymour Cray relied on compact innovative designs and local parallelism to achieve superior computational peak performance. However, in time the demand for increased computational power ushered in the age of massively parallel systems.
Here are some examples of supercomputer:
– IBM Roadrunner
– Cray Jaguar
– Fujitsu K computer
– IBM Sequoia
– Cray Titan
Advantages of supercomputer
The primary advantage that supercomputers offer is decreased processing time. Computer speed is commonly measured in “floating point operations,” or “FLOPS.” Average home computers can perform up to a hundred billion of these operations per second, or 100 “gigaflops.” Supercomputers, however, are tens of thousands of times faster, meaning that calculations that would take your home computer hours or days can be solved by a supercomputer in a matter of seconds.
Supercomputers are usually used to tackle large, real-world problems that would be too time consuming on regular computers. For example, weather forecasters use supercomputers to create models of the weather and to forecast the weather. Obviously, forecasts have to be made in a timely manner to make them useful so the more powerful the computer the better. Only supercomputers have the ability to perform these calculations in a timely fashion. One of the sayings of computing is that the higher the technology, the more trivial the application and the most powerful computers in the world are used by digital effects/computer animation companies. The sheer processing power of supercomputers means that they can be used to do things that ordinary computers simply couldn’t handle. Supercomputers have also permitted great strides in filmmaking and special effects.
Disadvantages of supercomputer
There have no great difference between mainframe computers because like the mainframe it takes up a large space and cost very high. It requires trained staff to can handle and use the supercomputer and it may only be good for specific application. It is high power consumption, it use a lot of electricity, for instance, about millions Rupees in a year.
Other disadvantage is that supercomputers require massive external storage drives whose bandwidth is fast enough to accommodate the data being analyzed and produced. If storage and bandwidth can’t keep up with the data flow, the supercomputer will not be able to work at its full capacity.
Unlike ordinary desktop computers that may finish calculating a problem in a few minutes or overnight, supercomputers work on tasks that require intensive calculations which can take extremely long periods to complete. For example, a supercomputer could spend months performing calculations to support research on climate change or to help cure a disease, presenting a disadvantage to people who are in a hurry for quick results.
After all we can say that computer has made his way since 19xx. It has begun with the microcomputer which consisted of simple technology. Then we have the minicomputer which becomes more and more personal and sophisticated for users. It makes great progress when the mainframe computer comes in 19xx (put the date). It comes with more performance and more memory with high security level. Their process increased more than 100 times and finally when the famous supercomputer comes which is 1000 times more powerful than the predecessor. And nowadays with the great evolution we have four type of computer.
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