Computer Basics Questions for SSC CGL

Generations of Computers

Computers evolved through five generations, each defined by the core technology used. Knowing the technology, speed, and era for each generation is enough for SSC CGL. Questions often ask which device belongs to which generation.

• 1st Generation (1940s-50s): Vacuum Tubes — ENIAC, UNIVAC. Very large, slow, hot.
• 2nd Generation (1950s-60s): Transistors — smaller, faster, less heat.
• 3rd Generation (1960s-70s): Integrated Circuits (ICs) — keyboard and monitor introduced.
• 4th Generation (1970s-present): Microprocessors (VLSI) — personal computers, Intel chips.
• 5th Generation (present-future): Artificial Intelligence, ULSI — voice recognition, parallel processing.

Types of Computers

Computers are classified by size and processing power. SSC CGL frequently asks you to match a computer type to its use case or size.

• Supercomputer: Fastest, used for weather forecasting, nuclear research. Example: PARAM (India).
• Mainframe: Used by large organizations like banks and airlines for bulk data processing.
• Minicomputer: Mid-range, used by departments within organizations.
• Microcomputer: Personal computers (PCs), laptops — most common type.
• Embedded Computer: Built into devices like washing machines, ATMs, cars.

Memory: RAM, ROM, and Storage

Memory is a very high-frequency area. You must know the difference between primary memory (RAM, ROM) and secondary storage (HDD, SSD, pen drive). RAM is volatile — data is lost when power goes off. ROM is non-volatile — data stays permanently.

• RAM (Random Access Memory): Volatile, temporary, used while running programs.
• ROM (Read Only Memory): Non-volatile, stores BIOS/firmware permanently.
• Cache Memory: Fastest memory, sits between CPU and RAM, very small in size.
• Secondary Storage: HDD, SSD, CD, DVD, Pen Drive — non-volatile, large capacity.
• Virtual Memory: Part of hard disk used as RAM when RAM is full.
• PROM, EPROM, EEPROM: Special ROMs — programmable or erasable variants.

Storage Units and Number System

Storage unit conversions are asked directly. Number systems (binary, decimal, octal, hexadecimal) appear less often but conversion questions do come in Quant or Computer sections. Learn the unit ladder by heart.

• 1 Byte = 8 Bits. 1 Kilobyte (KB) = 1024 Bytes.
• 1 Megabyte (MB) = 1024 KB. 1 Gigabyte (GB) = 1024 MB.
• 1 Terabyte (TB) = 1024 GB. 1 Petabyte (PB) = 1024 TB.
• Binary uses base 2 (0,1). Decimal uses base 10. Octal uses base 8. Hexadecimal uses base 16.
• 1 Nibble = 4 bits. 1 Word = 2 bytes (16 bits) typically.

Input and Output Devices

Input devices send data to the computer. Output devices receive processed data from the computer. Some devices like touchscreen and modem are both input and output. SSC CGL asks to classify specific devices.

• Input Devices: Keyboard, Mouse, Scanner, Microphone, Joystick, Barcode Reader, Webcam.
• Output Devices: Monitor, Printer, Speaker, Projector, Plotter.
• Both (I/O): Touchscreen, Modem, Headset with mic, Network Card.
• Plotter: Specialized output device used to print large engineering/architectural drawings.
• OCR (Optical Character Recognition): Reads printed text and converts to digital — input device.

Hardware vs Software

Hardware is anything physical you can touch. Software is a set of instructions you cannot touch. SSC CGL asks you to classify components and also tests knowledge of system software vs application software.

• System Software: Manages hardware — Operating System (Windows, Linux), Device Drivers, BIOS.
• Application Software: Performs user tasks — MS Word, Chrome, Photoshop, VLC.
• Utility Software: Maintenance tools — Antivirus, Disk Cleanup, File Compression (WinZip).
• Firmware: Software embedded into hardware (like ROM) — BIOS is best example.
• Open Source Software: Free, modifiable code — Linux, VLC, Firefox. Proprietary: MS Office, Photoshop.

CPU and Basic Architecture

The CPU (Central Processing Unit) is the brain of the computer. It has three main parts. Questions ask what each part does or which is the fastest memory component.

• ALU (Arithmetic Logic Unit): Performs all mathematical and logical operations.
• CU (Control Unit): Directs and coordinates all CPU operations — the traffic police of the CPU.
• Registers: Tiny, ultra-fast storage inside CPU for immediate data.
• Clock Speed measured in GHz — higher means faster processing.
• Bus: Data highway inside computer — Address Bus, Data Bus, Control Bus.

• Confusing RAM with ROM — remember RAM is temporary (like a whiteboard), ROM is permanent (like a printed book).
• Mixing up input and output for Modem and Touchscreen — these are BOTH. Do not mark them as only input or only output.
• Thinking 1 KB = 1000 Bytes — in computing it is 1024 Bytes (binary system), not 1000.
• Confusing ENIAC with the first stored-program computer — ENIAC is the first general-purpose electronic computer; EDSAC is first stored-program.
• Labeling Utility software as Application software — Antivirus and Disk Cleanup are Utility, not Application.

• Generations mnemonic: Very Tiny Integrated Micro Artificial — V T I M A (Vacuum Tubes, Transistors, ICs, Microprocessors, AI).
• Storage ladder: Baby Kittens Must Get Plenty of Treats — Bit, KB, MB, GB, PB, TB (reorder: Bit-Byte-KB-MB-GB-TB-PB).
• RAM vs ROM: RAM = Runs All the Moment (temporary, needs power). ROM = Remains On Memory (permanent).
• CPU parts: ACR — ALU does the math, CU Controls, Registers Remember instantly.

• SSC CGL typically asks 2-3 factual questions from Computer Basics in Tier 1 GA. These are free marks if memorized correctly.
• Most common question types: identify the generation by technology (vacuum tube = 1st), classify a device as input/output, identify volatile vs non-volatile memory.
• Storage unit conversion is sometimes disguised in GK as 'which is larger' type questions — know the sequence cold.
• Questions on India's supercomputers (PARAM series) and first computer in India (TIFRAC) come up occasionally — keep these as bonus facts.
• Do not spend more than 30-40 seconds per computer question in the exam. These are recall-based, so either you know it or you do not — move on quickly.