1.5 Anatomy of a Computer

 

     Programming in C    

1.5 Anatomy of a Computer

A computer can accept input, process or store data, and produce output according to a set of instructions. A computer system is divided into hardware and software.
Hardware refers to the tangible parts of the computer, whereas software is the intangible set of instructions that controls the hardware. Without software, a computer is useless.

1.5.1 Hardware

Hardware consists of all mechanical, electrical, electronic, and magnetic parts of a computer. The major hardware components are:

• Input and output devices

• Central Processing Unit (CPU)

• Memory unit and storage devices

• Interface unit

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Input Devices

Input devices are electronic or electro-mechanical devices used to feed data and instructions into a computer.

Keyboard

A keyboard consists of 104 keys arranged in a key matrix. The keys are classified as:

• Character keys – letters, numbers, punctuation

• Function keys – F1 to F12

• Control keys – Ctrl, Alt, Shift, Esc, etc.

• Navigation keys – Arrow keys, Home, End, PgUp, PgDn

• Toggle keys – Caps Lock, Num Lock, Scroll Lock

• Miscellaneous keys – Insert, Delete, Print Screen

When a key is pressed, the keyboard controller identifies the key using row and column coordinates and sends the code to the computer.

Mouse

A mouse is a pointing device used to move the cursor and select objects on the screen. It has two or three buttons and can be connected using USB or wirelessly. A wireless mouse uses batteries.

Scanner

A scanner captures documents or images so they can be stored, modified, transmitted, or printed. A computer with a scanner and printer can function as a photocopier.

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Output Devices

Output devices display or print the result of processing.

Monitor

A monitor (VDU) displays output. Common types are CRT and LCD.

• CRT monitors use electron beams and phosphor screens. They are bulky, consume high power, and emit radiation.

• LCD monitors use liquid crystal cells and are thinner, consume less power, and emit less radiation. LED displays use LED backlighting.

Printer

Printers produce hard copy output.

• Impact printer – Dot matrix printer

• Non-impact printer – Inkjet printer, Laser printer

Dot matrix printers strike the paper through a ribbon. Inkjet printers spray electrically charged ink droplets. Laser printers use a laser beam to create images.

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Central Processing Unit (CPU)

The CPU is the brain of the computer. It executes instructions, processes data, and controls operations. Physically, it is a silicon IC chip.

Components of CPU

• Registers – High-speed storage (IR, PC, general-purpose registers)

• Arithmetic Logic Unit (ALU) – Performs arithmetic and logical operations

• Control Unit (CU) – Controls data flow and instruction execution

Modern CPUs contain cache memory to improve performance.

CPU speed is measured in Hz, MHz, or GHz. Modern processors are multi-core, such as dual-core and quad-core processors.

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Memory Unit

Memory stores data and instructions in binary form.

Primary Memory

Primary memory (main memory) stores data during execution.

• RAM – Random Access Memory

• Volatile in nature

• Fast, expensive, limited capacity

Cache memory is a high-speed memory that stores frequently used data.

Secondary Memory

Secondary memory provides large, non-volatile, low-cost storage with slower access time.

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Memory Operations

• Read – Retrieves data

• Write – Stores data

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Units of Memory

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Word Size

Word size is the number of bits a CPU can process at a time. Common processors are 32-bit or 64-bit.

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Memory Hierarchy

From top to bottom:
Registers → Cache → Main Memory → Secondary Memory

Speed decreases and capacity increases down the hierarchy. Memory above secondary memory is volatile.

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Peripherals

Devices other than CPU and main memory are called peripherals, such as printers, scanners, cameras, and speakers.

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Interface Unit

The interface unit connects CPU, memory, and I/O devices using buses:

• Data bus – Carries data

• Address bus – Carries addresses

• Control bus – Carries control signals

Device controllers manage communication between CPU and I/O devices.

📖 Reference

The content for this subject is prepared by referring to the standard textbook “Computer Fundamentals and Programming in C” by Pradip Dey and Manas Ghosh, Second Edition, Oxford University Press (2018). The explanations are simplified and exam-focused while strictly aligning with the syllabus and concepts presented in the reference book.

Aivette‑coi is created with the intention of helping college students learn smartly, revise quickly, and approach exams with confidence.

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by Aivette 💙