Types of Computer Systems

Computer systems have undergone many changes recently. The invention of microprocessors with IC technology reduces large machines to small desktop computer systems. A number of computers are available with the same basic functions but all of these are not the same. computer systems can be categorized according to the application for which it is designed. Some are suitable for scientific calculations while others may be used to control appliances. Another way to categorize computer systems is according to their size and computing power.

1. Mainframes
2. Minicomputer
3. Microcomputer
4. Personal computer

Mainframes are high-speed computers and their word length generally ranges from 32 to 64 bits. They are capable of addressing Megabytes of memory and handling all types of peripherals and a large number of users. Mainframes are the largest and most powerful computers. Such a computer can fill an entire room. These are used in defense, image processing, science fiction movies, etc.

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Examples of this type of computer are IBM 4381 and the Honey well DP58. The fastest and most powerful mainframes are also known as supercomputers. Computers of this type are used for remote sensing, image processing, biomedical applications, weather forecasting, etc. Cray Y-MP/832 is a supercomputer that contains eight central processors with 64-bit word length and 32 million, 64-bit words of memory.

The scaled-down version of the mainframe computer with slower speed and smaller data words (often 32-bit words) is known as a minicomputer. This type of computer is smaller in size as compared to mainframes and can fit in a single rack or base. Digital Equipment Corporation VAX 6360, PDP 11/45, the Data General MV/8000 IT, and Nava are some examples of minicomputers. Such computers are used for large data processing and industrial control.

The microcomputer is a small computer that is designed using a microprocessor as its CPU. A microcomputer includes a microprocessor, memory, and input/output. Initially, microcomputers were designed with 8-bit microprocessors. Since then 16, 32, and 64-bit microprocessors such as the Intel 8086/88, 80286/386/486, Pentium Pro/P-4, and Motorola 68000, and the power PC 601 series have been designed. The use of these computers is spread in all the areas of small business applications, mathematical calculations, etc.

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Microcomputers can be further classified into four groups:

1. Personal Computer (PC)
2. Workstation
3. Single board microcomputer
4. Microcontroller (single-chip microcomputer)

A personal computer is a single-user system that can be used for a variety of purposes like keeping records of payroll, business accounts, word processing, and legal and medical record. IBM Personal Computer (PC 300 or PC 700) Apple computers and NCR 3000 series computers are a few examples of personal computers. According to the size, a personal computer can be further classified into three groups

1. Desktop computers
2. Laptop computers
3. Notebook computer

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A desktop computer is a 32-bit or 64-bit microcomputer with 32 to 64 MB system memory, a monitor, a 3(1/2) high-density floppy disk, and a hard disk with a storage capacity of more than 4 GB.

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A laptop computer is more portable than a desktop computer. This is having a flat screen, a hard disk, 3(1/2) floppy disks, and compact disk drives. This type of computer is lighter in weight and can be operated with battery and AC power.

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A notebook computer is a portable microcomputer. Notebook computers are smaller in size and lighter in weight. the size of a notebook computer is approx 8(1/2) x 11 x 2. A microcomputer smaller than a notebook computer, called a subnotebook or palmtop, is also available in the market.

The high-performance personal computer is named a workstation. workstations are specially configured for applications that require faster and more efficient data operations. workstations are designed with the RISC (Reduced Instruction Set Computing) processors. This type of computer has a storage memory of GB, system memory of more than 200 MB, and a high-resolution screen.

These microcomputers are primarily used in college laboratories and industries for instructional purposes or to evaluate the performance of a given microprocessor. These microcomputers are designed with 8 or 16-bit microprocessors, from 256 bytes to 2k bytes of user memory, a Hex keyboard, and seven-segment LEDs as a display.

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The interaction between the microprocessor, memory, and input/output is controlled by a small program which is named a monitor program. The function of the monitor program in a single-board microcomputer is similar to that of the operating system in a large system.

The microcontroller is a computer system in which all the system components (processor, memory, I/O ports) are fabricated on a single chip using VLSI technology. The microcontroller chip includes a microprocessor with 64 bytes of R/W memory, from 1k and 2k bytes of ROM, and several signal lines to connect I/Os. Microcontrollers are also known as single-chip microcomputers. Applications of this type are mainly in embedded systems. Zilog Z8, Intel MCS51, 96 series, and Motorola 68HCII are a few examples of microcontrollers.