Block Diagram of a Computer System : Explanation

 

🖥️ Block Diagram of a Computer System

📌 Text Diagram (Exam-Friendly)

┌─────────────┐
│ Input Unit  │
│ (Keyboard,  │
│ Mouse etc.) │
└──────┬──────┘
       ↓
┌─────────────┐
│     CPU     │
│ ┌─────────┐ │
│ │   CU    │ │
│ ├─────────┤ │
│ │   ALU   │ │
│ └─────────┘ │
└──────┬──────┘
       ↓
┌─────────────┐
│ Output Unit │
│ (Monitor,  │
│ Printer)   │
└─────────────┘
       ↑
┌─────────────┐
│   Memory    │
│ RAM / ROM  │
└─────────────┘

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🧩 Explanation of Each Part (With Diagram Reference)

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1️⃣ Input Unit

📍 Position in diagram: Left side (first block)

🔹 What it does:

• Accepts data and instructions from the user

• Converts them into machine-readable form

🔹 Examples:

• Keyboard

• Mouse

• Scanner

• Microphone

✍ Exam line:

👉 Input Unit sends data and instructions to the CPU for processing.

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2️⃣ Central Processing Unit (CPU)

📍 Position in diagram: Middle (main block)

The CPU is the brain of the computer. All processing happens here.

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🔸 A) Control Unit (CU)

📍 Inside CPU

Function:

• Controls all operations

• Tells input, memory, and output units what to do and when

✍ CU does not process data, it only controls.

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🔸 B) Arithmetic Logic Unit (ALU)

📍 Inside CPU

Function:

• Performs arithmetic operations ( + − × ÷ )

• Performs logical operations (>, <, =, AND, OR)

✍ ALU is responsible for calculations and decision making.

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3️⃣ Memory Unit

📍 Connected to CPU (bottom block)

🔹 What it does:

• Stores data, instructions, and results

• Supplies data to CPU when required

🔹 Types:

• RAM – Temporary, volatile

• ROM – Permanent, non-volatile

✍ Memory helps CPU by storing data during processing.

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4️⃣ Output Unit

📍 Position in diagram: Right side (last block)

🔹 What it does:

• Displays processed results to the user

• Converts machine output into human-readable form

🔹 Examples:

• Monitor

• Printer

• Speaker

✍ Output Unit presents the final result.

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🔁 Working of Computer (Flow Explanation)

1. Input Unit takes data

2. Data goes to CPU

3. CU controls the process

4. ALU performs calculations

5. Memory stores data/results

6. Output Unit shows the result

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⭐ 5-Mark Exam Answer (Ready-Made)

A computer system consists of Input Unit, CPU, Memory Unit, and Output Unit.
The Input Unit accepts data and instructions.
The CPU processes data with the help of CU and ALU.
The Memory Unit stores data temporarily or permanently.
The Output Unit displays the processed result to the user.