What is digital computer? Explain the components of digital computer with suitable block diagram.

A digital computer is an electronic device that works on discrete binary digits (0s and 1s). It accepts input, processes it through programmed instructions, and gives exact output. All modern PCs, laptops and smartphones are digital computers.

Components (block diagram):

Input Unit → CPU (ALU + CU + Registers) → Output Unit
                ↕
          Memory (Primary + Secondary)

1. Input Unit: Accepts data and instructions. Example: keyboard, mouse, scanner. 2. CPU — brain:

• ALU: Does arithmetic (+, −) and logic (>, <, =) operations.
• CU: Controls sequence — fetches, decodes and coordinates, does not process data itself.
• Registers: Tiny fast storage inside CPU for immediate values. 3. Memory:
• Primary: RAM (working) + ROM/BIOS (startup).
• Secondary: SSD/HDD for permanent storage. 4. Output Unit: Shows result. Example: monitor, printer, speaker.

Exam line: Input → Process (CPU) → Output, with memory supporting at every step.