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Block Diagram of a Computer

A computer works on the Input → Process → Output principle, supported by Storage and controlled by the Control Unit.

Main Components

1. Input Unit

  • Accepts data and instructions from the user.
  • Converts them into machine-readable form.
  • Examples: Keyboard, mouse, scanner, microphone.

2. Central Processing Unit (CPU)

Often called the “brain of the computer”, it consists of:

  1. Control Unit (CU):
    • Directs the flow of data and instructions.
    • Acts like a supervisor, ensuring operations are carried out in the right order.
  2. Arithmetic and Logic Unit (ALU):
    • Performs all arithmetic operations (add, subtract, multiply, divide).
    • Handles logical operations (comparisons like <, >, =).
  3. Registers:
    • Small, high-speed storage locations inside CPU for temporary data.

3. Memory / Storage Unit

  • Stores data, instructions, and results.
  • Two types:
    • Primary Storage (RAM, ROM): Fast, temporary storage.
    • Secondary Storage (Hard disk, SSD, Pen drive): Permanent storage.

4. Output Unit

  • Displays or provides results of processing to the user.
  • Converts machine-readable form into human-readable form.
  • Examples: Monitor, printer, speakers.

Block Diagram Representation

         ┌───────────┐
         │  Input    │
         │  Devices  │
         └─────┬─────┘
               │
               ▼
       ┌───────────────┐
       │   CPU         │
       │ ┌───────────┐ │
       │ │ Control   │ │
       │ │   Unit    │ │
       │ └────┬──────┘ │
       │      │         │
       │ ┌────▼──────┐ │
       │ │   ALU     │ │
       │ └───────────┘ │
       └───────┬───────┘
               │
         ┌─────▼─────┐
         │  Memory   │
         │ (Storage) │
         └─────┬─────┘
               │
               ▼
         ┌───────────┐
         │  Output   │
         │  Devices  │
         └───────────┘

Working Cycle

  1. Input: Raw data enters the system.
  2. Processing (CPU): CU controls flow, ALU performs operations.
  3. Storage: Data/results saved temporarily or permanently.
  4. Output: Final result shown to the user.

Summary for Students

  • A computer works like a system: Input → Process → Output, supported by Storage and Control Unit.
  • Block diagram is often asked in exams → Always label Input, CPU (CU + ALU), Memory, Output clearly.