SSC CGL Preparation – Day 1

Computer Basics – Organization of a Computer

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🔹 What is a Computer?

A computer is an electronic device that can process, store, and retrieve data according to instructions provided to it. It performs four main operations:

• Input: Receiving data.
• Processing: Manipulating data according to instructions.
• Storage: Saving data and instructions.
• Output: Producing results.

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🔹 Functional Organization of a Computer

A typical computer system is organized into five basic units:

Unit	Function
1. Input Unit	Takes input from user (e.g., keyboard, mouse).
2. Output Unit	Shows results to user (e.g., monitor, printer).
3. Memory/Storage Unit	Stores data and instructions (RAM, hard disk).
4. Control Unit	Manages and coordinates all units.
5. Arithmetic and Logic Unit (ALU)	Performs calculations and logical comparisons.

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🔹 Basic Components of a Computer

Component	Details
Hardware	Physical parts of a computer (CPU, RAM, Hard disk, Keyboard, Mouse).
Software	Set of instructions/programs to operate hardware and perform tasks (Windows, MS Word).
Firmware	Special software permanently stored in hardware (e.g., BIOS).
Humanware	People who use computers (users, programmers, technicians).

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🔹 Block Diagram of Computer Organization

Here’s how the different units work together:

mathematicaCopyEditInput Devices ➔ Central Processing Unit (CU + ALU) ➔ Memory ➔ Output Devices

• Input Devices: Feed data (Keyboard, Mouse, Scanner).
• Central Processing Unit (CPU):
  • Control Unit (CU): Directs operation.
  • Arithmetic and Logic Unit (ALU): Performs all calculations.
• Memory:
  • Primary Memory (RAM, ROM)
  • Secondary Memory (Hard disk, Pen drive)
• Output Devices: Display/print the results (Monitor, Printer).

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🔹 Characteristics of a Computer

Feature	Explanation
Speed	Processes millions of instructions per second.
Accuracy	Very high accuracy if programmed correctly.
Automation	Can perform tasks automatically once programmed.
Storage	Stores a huge amount of data permanently.
Versatility	Can perform different types of tasks.
Multitasking	Handles multiple tasks at once.
Diligence	No tiredness or lack of concentration.

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🔹 Types of Computers (Based on Size)

Type	Example	Features
Supercomputer	PARAM, IBM Summit	Extremely powerful, used for research.
Mainframe	IBM Z	Large organizations for bulk data.
Minicomputer	PDP-11	Mid-sized business tasks.
Microcomputer	Desktop, Laptop	Personal computers for everyday use.

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🔹 Conclusion

Understanding the organization of a computer gives you the base to explore more complex topics like memory, CPU functioning, and cyber security.
Remember the 5 core functional units and basic block diagram, as they are frequently asked in SSC exams.

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✍️ Important SSC CGL MCQ Keywords:

• ALU
• CU
• Input/output device examples
• Hardware vs Software
• Supercomputer vs Mainframe