Maarg Manthan · Topic 14.5

Types and Components of Computer Systems

Science & Technology › IT, Telecommunications and Computers · Topic 14.5

A computer system has hardware, which is the physical parts, and software, which is the set of programs that tells the hardware what to do. Hardware follows the von Neumann design of input devices, a central processing unit, memory, storage and output devices. The central processing unit has an arithmetic logic unit that does calculations, a control unit that directs operations and registers that hold data being used. Memory includes random access memory, which is fast and temporary, read-only memory, which keeps start-up instructions, and cache. Storage includes hard disks, solid state drives and optical discs. By size and power, computers are classed as microcomputers, minicomputers, mainframes and supercomputers, and by working principle as analog, digital and hybrid.

5 min read · UPSC Prelims · Science & Technology · IT, Telecommunications and Computers

At a Glance

Processing CPU with ALU and CU
Temporary memory RAM
Permanent memory ROM
Software System and application
Classes Micro, mini, mainframe, super
Exam link UPSC Prelims, Science & Technology: IT, Telecommunications and Computers

Where Does It Fit?

This topic follows the history of computers. It describes how a present-day computer is built and the kinds of computers in use, which prepares for later topics on displays, networks and security. Previous topic: History and Generations of Computers. Next topic: Display Technologies: Cathode Ray, LCD, LED, Plasma, OLED.

What Are the Parts of a Computer?

Part	Function
Input devices	Keyboard, mouse, scanner, microphone, touch screen, sensors. Send data to the computer
Central processing unit	The brain of the computer. Contains the arithmetic logic unit (calculation and comparison), the control unit (directing instructions) and registers (small fast storage)
Primary memory	RAM holds data and programs in use and loses its content when power is off. ROM holds permanent start-up instructions. Cache memory is a small fast store near the CPU
Secondary storage	Hard disk drives (magnetic), solid state drives (flash), optical discs and pen drives. Keep data permanently
Output devices	Monitor, printer, speakers, projector
Motherboard and buses	The main circuit board that connects all parts, with buses carrying data, addresses and control signals
Power supply	Converts mains power to the low voltages needed

How Are Computers and Software Classified?

Microcomputer: personal computers, laptops, tablets and smartphones, based on a microprocessor
Minicomputer: medium size multi-user machines of the 1960s to 1980s, now mostly replaced by servers
Mainframe: large, reliable computers used by banks, railways and insurers to handle huge numbers of transactions
Supercomputer: the fastest computers, used for weather, science and defence, as in Supercomputers and Their Applications
Analog, digital and hybrid: analog computers work with continuous signals, digital with binary numbers, hybrid combine both
System software: operating system (Windows, Linux, macOS, Android), device drivers and utilities
Application software: word processors, spreadsheets, browsers and games
Firmware: software stored in ROM or flash, such as the BIOS

What Else Should You Remember?

Bit and byte: a bit is a binary digit, 0 or 1, and eight bits make a byte
Units: 1 kilobyte is about 1,000 bytes, then megabyte, gigabyte, terabyte, petabyte and exabyte, each 1,000 times larger in decimal usage
Clock speed: measured in gigahertz, the number of cycles per second
Cores: modern CPUs have several cores that process tasks in parallel
GPU: graphics processing unit, specialised for parallel work such as graphics and artificial intelligence
Operating system functions: manages memory, files, devices, processes and the user interface
Volatile and non-volatile: RAM is volatile, while ROM, SSD and hard disks are non-volatile
Embedded systems: computers built into machines such as washing machines, cars and satellites
Servers and clients: servers provide services over a network, and clients use them
Open source: software whose code is public, such as Linux. India has promoted open source in e-governance
Hardware trends: shift to solid state storage, smaller devices and cloud services, as in Cloud Computing and Big Data
Link: history and generations are in History and Generations of Computers
Von Neumann architecture: John von Neumann described in 1945 a design in which both data and the program are stored in the same memory, and the CPU fetches and executes instructions one after another
Fetch-decode-execute cycle: the CPU repeats three steps endlessly: fetch an instruction from memory, decode what it means, and execute it
Bus types: the data bus carries data, the address bus carries memory locations and the control bus carries timing and command signals
Booting: when a computer is switched on, firmware in ROM runs a power-on test and loads the operating system from storage into RAM
Virtual memory: the operating system uses part of the disk as extra memory when RAM is full, at the cost of speed

Why Does It Matter for the Exam?

Components: CPU, ALU, CU, memory
Memory types: RAM, ROM, cache
Classes: micro, mini, mainframe, super
Current affairs link: AI chips and cloud servers
Common errors: saying RAM is permanent or that ALU controls the other units

As an analytical point, knowing the parts of a computer helps in understanding security, cloud and AI topics later. The line between types of computers is blurring as phones now match the power of old desktops.

Why Is This Topic Important?

Parts CPU and memory
Memory RAM versus ROM
Classes By size

What Came Next?

The next topic covers display technologies such as CRT, LCD, LED, plasma and OLED. Next topic: Display Technologies: Cathode Ray, LCD, LED, Plasma, OLED.

Key People and Terms

CPU Central processing unit
ALU Arithmetic logic unit
RAM Random access memory
ROM Read-only memory
OS Operating system
Byte Eight bits

Exam Corner

Points to Remember

CPU = ALU + control unit + registers.
RAM is volatile; ROM is non-volatile.
1 byte = 8 bits.
Von Neumann: stored program.
Mainframes handle transactions.

Do Not Confuse With

RAM and ROM Temporary working memory versus permanent start-up memory
Hardware and software Physical parts versus programs
System and application software Runs the machine versus does user tasks

Memory Hook

Input, process, store, output; the CPU has ALU and CU; RAM forgets, ROM remembers.

Mains Angle

Questions ask for components and memory types. These points help.

Parts Von Neumann model
Classes By size and use
Trend Cloud and mobile

A Question You May Face

An original practice question, not a past paper question.

“Describe the components of a computer system and the classification of computers.”

How to Answer

Parts Input to output.
CPU ALU, CU.
Memory RAM, ROM.
Types Micro to super.

GS Relevance

Prelims: components, memory types, units, classification of computers. GS Paper 3: science and technology, IT.

Frequently Asked Questions

What are the main components of a computer?

A computer has input devices such as a keyboard and mouse, a central processing unit with an arithmetic logic unit, control unit and registers, primary memory such as RAM and ROM, secondary storage such as hard disks and solid state drives, and output devices such as a monitor and printer, connected on a motherboard.

What is the difference between RAM and ROM?

Random access memory is fast, temporary memory that holds programs and data currently in use and loses its contents when the power is switched off. Read-only memory is permanent memory that keeps start-up instructions and is not lost when power goes off. RAM is volatile and ROM is non-volatile.

What does the CPU do?

The central processing unit fetches instructions from memory, decodes them and carries them out. Its arithmetic logic unit performs calculations and comparisons, its control unit directs the flow of data between the CPU, memory and devices, and its registers hold the data being processed at the moment.

What is an operating system?

An operating system is system software that manages the hardware and other software of a computer. It controls memory, files, devices and running programs, and provides the user interface. Windows, Linux, macOS and Android are examples, and applications run on top of the operating system.

How are computers classified by size?

By size and power, computers are classified as microcomputers, such as laptops and smartphones, minicomputers, which are medium size multi-user machines, mainframes, which are large machines for heavy transaction processing in banks and railways, and supercomputers, which are the fastest machines used for scientific and defence calculations.

PYQ Practice — Statement Analysis

1 RAM is a non-volatile memory.

False

It loses data when power is off.

2 The arithmetic logic unit is a part of the CPU.

True

Along with the control unit.

3 One byte is equal to eight bits.