What is the difference between hardware and software?

Hardware is the physical part you can touch, like the CPU, monitor and hard disk. Software is the set of programs that tell the hardware what to do, like Windows or MS Word.

What are the three parts of a CPU?

The Arithmetic Logic Unit (ALU), the Control Unit (CU) and the memory (storage) unit with its registers.

Which part of the CPU controls all other parts?

The Control Unit (CU). It fetches and decodes instructions and sends signals to memory, the ALU and the input-output devices.

What are the five generations of computers?

First: vacuum tubes. Second: transistors. Third: integrated circuits. Fourth: microprocessors (VLSI). Fifth: ULSI chips and artificial intelligence.

What is the full form of ENIAC?

Electronic Numerical Integrator And Computer. It was built by J. Presper Eckert and John Mauchly at the University of Pennsylvania and shown to the public in 1946.

Who gave the stored-program concept?

John von Neumann, in his 1945 report on the EDVAC. In this design one memory holds both the data and the program.

Is Android system software or application software?

Android is an operating system, so it is system software. A compiler is also system software. Browsers and Photoshop are application software.

Which language does a computer understand directly?

Machine (binary) language, written only in 0s and 1s. It needs no compiler, interpreter or assembler.

Which flowchart symbol shows a decision?

The diamond. It holds a condition and has two exits, usually Yes and No. An oval shows start or end, and a rectangle shows a process.

Punjab Police ASI Computer Fundamentals — Computer Basics: Hardware, Software, CPU and Generations Notes

Q: What is a computer in simple words?

A computer is an electronic machine that takes input, processes it by following instructions, gives output and stores data. It works with binary numbers (0 and 1).

Two programmers setting cables and switches on the large panels of the ENIAC computer — Glen Beck and Betty Snyder program the **ENIAC** (Electronic Numerical Integrator And Computer). ENIAC filled a whole room. Today a phone chip is far more powerful. Image: U.S. Army photo, Wikimedia Commons · Public domain

A computer is an electronic machine. It takes input, processes it by following instructions, gives output and stores the result. It works only with 0 and 1 (binary). This page covers the basics that Punjab Police SI and Constable papers ask again and again: parts of a computer, hardware and software, what happens inside the CPU, the five generations, programming languages and common full forms.

60+

Past questions on this page

Punjab Police SI & Constable

5

Generations of computers

Tube → transistor → IC → chip → AI

1947

Transistor invented

Bell Labs, USA

3

Parts of the CPU

ALU, CU, memory unit

What a computer is and what it does

Five functions and eight qualities. Easy marks.

HOW EVERY COMPUTER WORKS

Input
You enter data and instructions (keyboard, mouse).
CPU
Processing
The CPU works on the data.
Output
You get the result (screen, printer).
Storage
Data and results are saved for later.

This is called the input–process–output cycle.

Function	What it means
Inputting	Entering data and instructions into the computer
Storing	Saving data and instructions so they are ready for processing
Processing	Doing arithmetic and logic work on the data
Outputting	Giving the result to the user
Controlling	Directing the order in which all the steps happen

KEY TERM

Binary and Boolean logic

Modern digital computers store everything as 0s and 1s (binary). They decide with Boolean logic (true/false, AND, OR, NOT). They do not use continuous (analog) signals for their work.

0 and 1→Boolean logic→digital computer

Quality

Speed

Millions of steps each second. Measured in MIPS (Millions of Instructions Per Second).

Quality

Accuracy and reliability

Gives correct results if the input and program are correct.

Quality

Diligence and versatility

Never gets tired or bored. Can do many kinds of work.

Quality

Power of remembrance

Stores data and gives it back whenever needed.

Limit

No IQ, no feelings

Cannot think for itself. It does nothing without instructions.

Installation is not a quality of a computer. It is a job you do on it.

Where computers are used: banking (online transactions, fraud checks), ATM (Automated / Automatic Teller Machine), weather forecasting, gaming, and education (online learning platforms).
A job done fully by hand, like laying bricks manually, is not a computer application.

QUICK CHECK

Which of the following is NOT a characteristic of a computer?

Tap an option to answer

QUICK CHECK

Match the functions with their meaning. I. Inputting, II. Storing, III. Controlling — 1. Saving data and instructions for processing, 2. Directing the order of operations, 3. Entering data and instructions.

Tap an option to answer

Hardware, software and firmware

What you can touch, what you cannot, and the layers in between.

THREE WORDS THAT GET MIXED UP

Hardware

Software

Firmware

What it is

Physical parts you can touch

Programs; cannot be touched

Fixed program inside a device

Examples

CPU, monitor, hard disk

Windows, MS Word

BIOS, phone firmware

Lives in

The machine itself

Disk / memory

ROM / flash chip

Monitor (visual display unit), CPU and storage device are hardware. Software is not a physical part.

THE LAYERS OF A COMPUTER SYSTEM (OUTSIDE TO INSIDE)

User
You.
Application software
Programs for your work: word processor, browser, Photoshop.
System software
Runs the machine: operating system, drivers, translators.
core
Hardware
The physical machine at the centre.

If a diagram leaves the innermost box blank, the answer is hardware.

SYSTEM SOFTWARE

Operating systems: Windows, Android, Linux
Device drivers
Language translators: compiler, interpreter, assembler (e.g. Java compiler)
Its job: manage and control the hardware

APPLICATION SOFTWARE

Word processors: MS Word, KWrite (Linux), Pages (Mac)
Spreadsheets: Excel, Numbers (Mac)
Presentation: PowerPoint, Keynote (Mac)
Others: Microsoft Edge (browser), Adobe Photoshop, Zoom, Webex

KEY TERM

Firmware and BIOS

Firmware is a program written permanently into a device's chip. It runs the basic work of that hardware, for example in a smartphone. It is made for that one device. BIOS (Basic Input Output System) is the firmware on a computer's motherboard. When you switch on, it checks the hardware and starts loading the operating system. This start-up is called booting.

Power on→BIOS checks hardware→OS loads

Part	Inside or peripheral?	Note
Mouse, keyboard, printer	Peripheral	Attached from outside to give input or take output
CPU, RAM, hard disk	Core parts	Processing chips, internal memory and storage
VGA card	Expansion card	Also called video / display card or graphics adapter. Makes the picture for the monitor.
NIC	Expansion card	Network Interface Card: connects to a network

A single computer = CPU chips + internal memory + I/O devices and peripherals.

QUICK CHECK

Which of the following are examples of system software? (i) Microsoft Edge (ii) Android (iii) Java Compiler (iv) Adobe Photoshop

Tap an option to answer

QUICK CHECK

Which statement(s) about firmware is/are NOT correct? I. Firmware runs the basic operations of a smartphone's hardware. II. Firmware is closely tied to its particular device.

Tap an option to answer

Inside the CPU

ALU, CU, registers and buses: the brain of the computer.

A square processor chip sitting in its socket on a computer motherboard — A modern CPU in its socket on the motherboard. This one is an eight-core processor: one chip, eight cores working side by side. Image: Brian Wong, Wikimedia Commons · CC BY-SA 2.0

ALU

Arithmetic Logic Unit

Does the sums (+ − × ÷) and the comparisons (greater, equal, AND/OR).

CU

Control Unit

Manages and coordinates all other parts. Fetches and decodes each instruction.

Memory

Storage (memory) unit

Holds the data and instructions to be processed, and the intermediate results.

The CPU's main job is processing data, not input, output or long-term storage.

THE MACHINE CYCLE: WHAT THE CPU DOES AGAIN AND AGAIN

Fetch
The CU takes the next instruction from memory. The program counter tells it where.
Decode
The instruction sits in the instruction register and is understood.
Execute
The ALU does the work.
Store
The result goes back to a register or memory.

Register	What it holds
Program Counter (PC), also "program control register"	Address of the next instruction
Instruction Register (IR)	The instruction being executed now
Memory Address Register (MAR)	Address of the memory location being used
Memory Data / Buffer Register (MDR / MBR)	The data being read from or written to memory

REMEMBER

PC = Pointing to the Coming one (next instruction). IR = In Running (current instruction).

THE THREE BUSES (ROADS FOR SIGNALS)

Data bus

Address bus

Control bus

Carries

The data itself

Where to read/write

Read, write, timing signals

Direction

Both ways

CPU → memory

Both ways

There is no "security bus". Only these three make up the system bus.

64-bit vs 32-bit: the big gain of a 64-bit processor is that it can directly use much more RAM. A 32-bit system is limited to about 4 GB.
Multicore processor: one chip with two or more cores. It handles more work in parallel and runs many programs (threads) at the same time.
Backward compatible: a new CPU that still understands all the instructions of the older CPU, plus some new ones.
The CPU can be on one or more microchips called integrated circuits.

QUICK CHECK

Which part of the computer system manages and coordinates the operations of all the other parts?

Tap an option to answer

QUICK CHECK

Which register holds the instruction that the CPU is executing right now?

Tap an option to answer

QUICK CHECK

The computer bus which is NOT used to transfer data between components of a computer is:

Tap an option to answer

Before modern computers: the pioneers

Pascal, Babbage, Hollerith, von Neumann and the ENIAC.

A brass box with a row of number wheels on top: Pascal's calculator

A tall machine of brass gears and columns in a glass case

Who's who

Charles Babbage

1791–1871 · Called the father of the computer

Designed the Difference Engine and the Analytical Engine
The Analytical Engine had the idea of a mill (processor) and a store (memory)

Unknown photographer, Wikimedia Commons · Public domain

Herman Hollerith

1860–1929 · Punched-card tabulating machine

His tabulating machine counted the 1890 US census
Called the first step towards programming

Charles Milton Bell, Wikimedia Commons · Public domain

John von Neumann

1903–1957 · Stored-program concept

Said one memory should hold both the data and the program (1945 report on the EDVAC)
Most computers today still follow this "von Neumann" design

Los Alamos National Laboratory, Wikimedia Commons · Attribution (LANL)

A long room lined with ENIAC's tall panels of switches and cables — **ENIAC = Electronic Numerical Integrator And Computer.** Built by J. Presper Eckert and John Mauchly at the University of Pennsylvania, USA, and shown to the public in 1946. It used vacuum tubes. Image: U.S. Army photo, Wikimedia Commons · Public domain

FROM ADDING MACHINE TO SMARTPHONE

1642
Pascaline
Blaise Pascal's mechanical adding machine.
1830s
Analytical Engine
Charles Babbage designs a general-purpose machine.
1890
Tabulating machine
Hollerith's punched cards count the US census.
1945
Stored-program idea
John von Neumann's report on the EDVAC.
1946
ENIAC
The famous vacuum-tube computer is shown to the public.
1947
Transistor
Invented at Bell Labs, USA, from semiconductor material.
1971
Intel 4004
An early single-chip microprocessor.
2007
First iPhone
Apple introduces its first iPhone.

QUICK CHECK

______ is considered the first step towards programming, and it was designed by Herman Hollerith.

Tap an option to answer

QUICK CHECK

Who introduced the concept of the stored-program computer, which could store both data and programs in memory?

Tap an option to answer

The five generations of computers

Each generation is named after the part that did the switching.

A row of glass vacuum tubes of different sizes

Replica of the first transistor under a glass dome

Generation	About when	Main technology	Languages and other marks
First	1940s–1956	Vacuum tubes	Machine language. Punched cards and paper tape; magnetic tape use began. ENIAC, UNIVAC.
Second	1956–1963	Transistors	Assembly language and early high-level languages (FORTRAN, COBOL).
Third	1964–1971	Integrated circuits (IC)	High-level languages such as PL/1, PASCAL, BASIC. Keyboards, monitors, operating systems.
Fourth	1971 onwards	Microprocessors (VLSI)	Personal computers, GUI, networks.
Fifth	Present and future	ULSI chips, artificial intelligence	ULSI puts about ten million parts on one chip. Voice and natural-language input.

Books give slightly different years for each generation. Learn the technology; that is what papers test.

REMEMBER

"Very Tall Indian Men Act" = Vacuum tube → Transistor → IC → Microprocessor → AI (ULSI).

COMMON TRAPS

VLSI vs ULSI: VLSI (very large-scale) = 4th generation. ULSI (ultra large-scale) = 5th generation.
The transistor was invented in 1947, but second-generation computers came later. Don't mark 1947 as the first generation.
A microchip is an integrated circuit, not a single transistor or capacitor.

QUICK CHECK

Computers of which generation were made using transistors?

Tap an option to answer

QUICK CHECK

Which fifth-generation technology produces microprocessor chips with ten million electronic components?

Tap an option to answer

QUICK CHECK

Use of magnetic tapes as input and output devices started in the ______ generation of computers.

Tap an option to answer

Programming languages and translators

From 0s and 1s to Python, and the flowchart symbols.

Level	Written as	Translator needed
Machine (binary) language	Only 0s and 1s	None: the CPU understands it directly
Assembly language	Short codes like ADD, MOV	Assembler
High-level language	English-like words: C, Java, Python	Compiler or interpreter

COMPILER VS INTERPRETER

Compiler

Interpreter

Translates

The whole program at once

One line at a time

Errors shown

After translating all

Line by line

Both are system software, like the assembler.

Source program: the program as the programmer writes it, in a high-level language. The translator turns it into an object program in machine language.
IDE (Integrated Development Environment): one software with a text editor, build tools and a debugger.

Science

FORTRAN

FORmula TRANslation. Made at IBM (1957) for scientific and number work.

Statistics

R

Mainly used in statistical software.

Data science

Python

The language most used in data science today.

Object-oriented

C++

A popular general-purpose object-oriented language (C with classes).

Flowchart symbol	Used for
Oval	Start / end
Parallelogram	Input / output
Rectangle	A process or step
Diamond	A decision (Yes / No)
Arrows	Direction of flow

QUICK CHECK

______ does not need any interpreter or compiler, because the computer understands these signals directly.

Tap an option to answer

QUICK CHECK

The decision function in flowcharting is represented by:

Tap an option to answer

Types of computers, interfaces and codes

PC to supercomputer, CLI to voice, and ASCII.

A tall round Cray supercomputer with a bench-like base in a computer room — A **Cray supercomputer** at a US research facility. Supercomputers are the fastest kind, used for work like weather forecasting. Image: Unknown photographer, Wikimedia Commons · Public domain

Type	In simple words
Personal computer (PC)	Single-user, with a moderately powerful microprocessor
Mini computer	Serves several users at once; smaller than a mainframe
Mainframe	Large machine for hundreds of users, e.g. banks
Supercomputer	Fastest; heavy science work

WAYS TO TALK TO A COMPUTER (USER INTERFACES)

CLI

GUI

VUI

Full form

Command Line Interface

Graphical User Interface

Voice User Interface

You use

Typed commands

Windows, icons, mouse

Your voice

Example

MS-DOS

Windows

Voice assistants

"Task user interface" is not a real interface type. Text (command) mode is cumbersome, slow and limited, which is why GUIs took over.

KEY TERM

ASCII

American Standard Code for Information Interchange. A 7-bit code, so it has 2⁷ = 128 codes (0–127). It gives a number to each letter, digit, punctuation mark and control character.

A→65→1000001

QUICK CHECK

Which of the following is a single-user computer system that has a moderately powerful microprocessor?

Tap an option to answer

QUICK CHECK

Which one of the following is NOT a valid user-computer interface?

Tap an option to answer

Quick revision

Full forms, traps and one-line facts.

FLASHCARDS

Full forms: tap to check

CPU: Central Processing Unit
ALU: Arithmetic Logic Unit
ENIAC: Electronic Numerical Integrator And Computer
BIOS: Basic Input Output System
GUI: Graphical User Interface
ASCII: American Standard Code for Information Interchange
MIPS: Millions of Instructions Per Second
IDE: Integrated Development Environment
ATM: Automated / Automatic Teller Machine
DLP (3D printing): Digital Light Processing
IMEI: International Mobile Equipment Identity
ULSI: Ultra Large-Scale Integration

COMMON TRAPS

PC vs IR: PC = address of the next instruction; IR = the current instruction.
Android is system software (an operating system), not an app.
A compiler is system software; a word processor is not.
Mouse is a peripheral; CPU, RAM and hard disk are core parts.
Monitor size does not change computer speed.

Also asked onceTap to open

Apple introduced its first iPhone in 2007.
Dial *#06# to see your phone's IMEI number (15 digits).
.AU is a basic audio file type supported by Windows. (.GIF is an image, .BAT is a batch file.)
KWrite is a text / word-processing program on Linux (KDE).
DLP in 3D printing = Digital Light Processing.
Both are true: operating systems and device drivers are system software, and system software manages and controls hardware.

CHECK YOURSELF

Name the three parts of the CPU and say what each does in one line.

Show answer

ALU does arithmetic and logic. CU controls and coordinates all parts. The memory unit holds data, instructions and intermediate results.

Computer Basics: Hardware, Software, CPU and the Five Generations

What a computer is and what it does

Hardware, software and firmware

Inside the CPU

Before modern computers: the pioneers

The five generations of computers

Programming languages and translators

Types of computers, interfaces and codes

Quick revision

Frequently Asked Questions

What is a computer in simple words?

What is the difference between hardware and software?

What are the three parts of a CPU?

Which part of the CPU controls all other parts?

What are the five generations of computers?

What is the full form of ENIAC?

Who gave the stored-program concept?

Is Android system software or application software?

Which language does a computer understand directly?

Which flowchart symbol shows a decision?