Introduction to Computers & Types
A computer is an electronic device that takes input, processes it, and gives useful output. Understanding what a computer is and how it is classified is the very first thing tested in the STS BPS-14 exam.
A. What is a Computer?
Definition & Key People
Origin of the word and founders of computing
| Point | Detail |
|---|---|
| Word Origin | Latin word "computare" = to calculate. First used in 1613 to describe a person who does calculations. |
| Definition | An electronic device that accepts input, processes it, stores results, and produces output — following the IPO Cycle (Input → Process → Output). |
| Programmable | The same machine can do different tasks by running different programs. A computer only does what it is told — it has no intelligence of its own. |
| Father of Computer | Charles Babbage — designed Difference Engine (1822) and Analytical Engine (1830s) |
| Father of Computer Science | Alan Turing — proposed the universal computing machine (Turing Machine) |
| First Programmer | Ada Lovelace — wrote first algorithm for Babbage's Analytical Engine |
| First Electronic Computer | ENIAC (1945) — built by J. Presper Eckert & John Mauchly, University of Pennsylvania |
Word Origin
OriginLatin word "computare" = to calculate. First used in 1613 to describe a person who does calculations.
Definition
MeaningAn electronic device that accepts input, processes it, stores results, and produces output — the IPO Cycle.
Programmable
Key pointThe same machine can do different tasks by running different programs. A computer only does what it is told — it has no intelligence of its own.
Father of Computer
PersonCharles Babbage — Difference Engine (1822) and Analytical Engine (1830s)
Father of Computer Science
PersonAlan Turing — proposed the Turing Machine (universal computing concept)
First Programmer
PersonAda Lovelace — wrote first algorithm for Babbage's machine
First Electronic Computer
Name & YearENIAC (1945) — built by Eckert & Mauchly, University of Pennsylvania
⚡ Exam Tip — "Computer" = Latin (not German or French). Charles Babbage = Father of Computer. Alan Turing = Father of Computer Science. Both come up frequently in MCQs.
B. Characteristics of a Computer
What Makes Computers So Powerful?
Six key characteristics that define computer performance
Speed
Processes billions of cycles per second (GHz). Can handle millions of instructions per second (MIPS) — far beyond any human.
Accuracy
Produces correct results as long as input is correct. Wrong input = wrong output. This is called GIGO (Garbage In, Garbage Out).
Storage
Stores enormous data permanently (HDD) and temporarily (RAM). Retrieves any piece of data in fractions of a second.
Diligence
Never gets tired or bored. Performs the same task a million times with exactly the same accuracy — unlike humans.
Versatility
One machine does many different tasks just by changing the software — design, writing, accounting, gaming, music.
No Intelligence
Cannot think, judge, or decide. Only follows instructions. Humorously called "Sillico Sapiens" but has no real intelligence.
⚡ Exam Tip — "Are computers infallible?" Answer: No. They are reliable but NOT infallible. Errors happen due to wrong input (GIGO) or software bugs.
C. Types of Computers — By Size
From Smallest to Largest
Micro → Mini → Mainframe → Super
| Type | Also Called | Description | Examples |
|---|---|---|---|
| Microcomputer | Personal Computer (PC) | Smallest type. Uses a microprocessor as CPU. Designed for one user at a time. Most common — used in homes and offices. | Desktop, Laptop, Tablet, Smartphone |
| Minicomputer | Mid-range Computer | Medium-sized. Faster than microcomputer. Supports multiple users at once. Used in universities and factories. | DEC PDP series, IBM AS/400 |
| Mainframe | Big Iron | Very large & powerful. Handles thousands of users simultaneously. Used by banks, insurance companies, and government. | IBM z15, Unisys Clearpath |
| Supercomputer | — | Fastest and most powerful. Used for weather forecasting, nuclear research, space simulation. Speed measured in FLOPS. | Fugaku (Japan), Summit (USA) |
Microcomputer (PC)
SizeSmallest type. Uses a microprocessor as its CPU.
UsersDesigned for one user at a time.
ExamplesDesktop, Laptop, Tablet, Smartphone
Minicomputer
SpeedFaster than microcomputer.
UsersSupports multiple users at once.
ExamplesDEC PDP series, IBM AS/400
Mainframe Computer
UsersHandles thousands of users simultaneously.
Used byBanks, insurance companies, government
ExamplesIBM z15, Unisys Clearpath
Supercomputer
SpeedFastest and most powerful. Speed measured in FLOPS.
Used forWeather forecasting, nuclear research, space simulation
ExamplesFugaku (Japan), Summit (USA)
⚡ Exam Tip — Size order: Micro → Mini → Mainframe → Super. Supercomputer = fastest. Mainframe = most users at once. Minicomputer is faster than Microcomputer.
Portable Computers
Microcomputers you can carry around
| Type | Description |
|---|---|
| Laptop / Notebook | Portable PC with built-in screen, keyboard, and battery. |
| Tablet | Touchscreen-based portable device. No physical keyboard. |
| PDA (Palmtop) | Personal Digital Assistant — handheld/pocket-sized computer. Mostly replaced by smartphones. |
| Smartphone | Mobile phone with full computing capabilities. Runs Android or iOS. |
Laptop / Notebook
Portable PC with built-in screen, keyboard, and battery.
Tablet
Touchscreen-based. No physical keyboard.
PDA (Palmtop / Handheld)
Personal Digital Assistant — pocket-sized computer, mostly replaced by smartphones.
Smartphone
Mobile phone with full computing capabilities. Runs Android or iOS.
D. Types of Computers — By Working Principle
Analog, Digital & Hybrid
Based on how the computer processes data internally
| Type | Data Form | Key Point | Examples |
|---|---|---|---|
| Analog | Continuous electrical signals | Input is NEVER converted to digital. Works by measuring, not counting. Processes physical quantities. | Thermometer, Speedometer, Seismograph |
| Digital | Binary (0s and 1s) | Works by counting. Fast, accurate, versatile. Most computers today are digital. | Laptops, Desktops, Smartphones |
| Hybrid | Both continuous AND binary | Combines analog + digital. Can measure AND count. Used in specialized applications. | Hospital ICU monitors, Flight simulators, Petrol pumps |
Analog Computer
Data formContinuous electrical signals
Key pointInput is NEVER converted to digital form. Works by measuring, not counting.
ExamplesThermometer, Speedometer, Seismograph
Digital Computer
Data formBinary — 0s and 1s
Key pointWorks by counting. Fast, accurate, versatile. Most computers today are digital.
ExamplesLaptops, Desktops, Smartphones
Hybrid Computer
Data formBoth continuous and binary
Key pointCombines analog + digital. Can measure AND count.
ExamplesHospital ICU monitors, Flight simulators
⚡ Exam Tip — "In analog computer, input is NEVER converted to digital." Digital clock = digital device. Clock with hands = analog. Most computers today = Digital.
Interactive Visualiser — Click Any Type
See each computer type illustrated with key specs
Microcomputer
The most common computer. Uses a microprocessor as its CPU. Designed for one user at a time. Used at home, school, and office.
Examples: Laptop, Desktop, Tablet, Smartphone
E. Hardware vs Software
Hardware vs Software Comparison
Physical components vs programs and instructions
| Feature | Hardware | Software |
|---|---|---|
| Definition | Physical components you can touch and see | Programs and instructions that tell hardware what to do — cannot be touched |
| Nature | Tangible (physical) | Intangible (non-physical) |
| Input devices | Keyboard, Mouse, Scanner, Microphone, Webcam | — |
| Output devices | Monitor, Printer, Speaker, Projector | — |
| Processing | CPU (ALU + Control Unit), RAM, Registers | — |
| Storage devices | Hard Disk, SSD, USB Drive, CD/DVD | — |
| System software | — | OS (Windows, Linux, Android), Device drivers |
| Application software | — | MS Word, Chrome, Photoshop, Games |
| Firmware | — | Stored permanently in ROM — e.g. BIOS (starts the computer) |
Hardware
NaturePhysical, tangible — you can touch it.
ExamplesKeyboard, Monitor, CPU, RAM, Hard Disk, Printer
Software
NatureNon-physical, intangible — you cannot touch it.
TypesSystem software (OS) and Application software (MS Word, games)
Firmware
What it isSoftware stored permanently in ROM. Example: BIOS — starts the computer on power-on.
⚡ Exam Tip — Physical structure of computer = Hardware. Programs = Software. BIOS in ROM = Firmware.
Inside the CPU & Memory
CPU = ALU + Control Unit
| Component | Full Name | Function |
|---|---|---|
| ALU | Arithmetic Logic Unit | Performs all arithmetic (+, −, ×, ÷) and all logical operations (AND, OR, NOT). Has 2 sub-units: Arithmetic Unit + Logic Unit. |
| CU | Control Unit | Directs and coordinates all CPU operations — fetches instructions, decodes them, controls execution. |
| Registers | — | Very small, very fast temporary storage inside the CPU. Holds data currently being processed. |
| Cache | — | High-speed buffer between RAM and CPU. Stores frequently used data to speed up processing. |
| RAM | Random Access Memory | Temporary (volatile) — data lost when power is off. Holds programs and data while in use. |
| ROM | Read-Only Memory | Permanent (non-volatile) — data stays without power. Stores BIOS/firmware. |
ALU — Arithmetic Logic Unit
Performs all arithmetic (+, −, ×, ÷) and logical operations (AND, OR, NOT).
CU — Control Unit
Directs and coordinates all CPU operations. Fetches and decodes instructions.
Registers
TypeVery small, very fast temporary storage inside the CPU. Holds data currently being processed.
Cache
TypeHigh-speed buffer between RAM and CPU. Stores frequently used data to speed up processing.
RAM — Random Access Memory
TypeTemporary / Volatile — data lost when power is off.
ROM — Read-Only Memory
TypePermanent / Non-volatile — data stays without power. Stores BIOS (firmware).
⚡ Exam Tip — CPU = ALU + Control Unit. RAM = temporary (volatile). ROM = permanent (non-volatile). 1 Byte = 8 bits. Motherboard = main circuit board holding CPU, RAM, and all components.
Quick Fire Revision
- "Computer" derived fromLatin
- Father of ComputerCharles Babbage
- Father of Computer ScienceAlan Turing
- World's first programmerAda Lovelace
- First electronic computer (1945)ENIAC
- Brain of a computerCPU
- CPU consists ofALU + Control Unit
- Most powerful computer typeSupercomputer
- Handles thousands of users at onceMainframe
- PC = Personal Computer =Microcomputer
- Palmtop / Handheld =PDA
- Analog computer input isNever converted to digital
- Combines analog + digitalHybrid computer
- Most computers today areDigital
- Physical parts of computerHardware
- Programs stored in ROMFirmware (BIOS)
- 1 Byte =8 bits
- RAM isTemporary / Volatile
- GIGO =Garbage In, Garbage Out
- CPU speed measured inMHz or GHz