Computer Fundamentals

Definition: A computer is an electronic device that accepts data (input), processes it, stores it, and produces information (output).

Core Parts

• CPU (Central Processing Unit) — the "brain"; has the ALU (arithmetic & logic) and Control Unit.
• Input devices — keyboard, mouse, scanner.
• Output devices — monitor, printer, speakers.
• Storage — hard disk, SSD, pen drive.

Hardware vs Software

• Hardware — the physical parts you can touch.
• Software — the programs and instructions (system and application software).

Real-world example: When you type a document, the keyboard is input, the CPU processes it, the screen is output, and the disk stores the file.

Example 1. The "brain" of the computer is the:

• CPU (Central Processing Unit).

Example 2. Which of these is an input device: monitor, printer, keyboard, speaker?

• Keyboard.

Example 3. The ALU inside the CPU performs:

• Arithmetic and logical operations.

Definition: Memory holds data and instructions. It is divided into primary (main) memory and secondary (storage) memory.

Primary Memory

• RAM (Random Access Memory) — temporary, volatile (lost when power is off); holds currently-running programs.
• ROM (Read Only Memory) — permanent, non-volatile; stores start-up instructions.

Secondary Storage

Hard disk, SSD, pen drive, CD/DVD — permanent, larger, slower than RAM.

Units (smallest → largest)

Bit → Byte → KB → MB → GB → TB. 1 Byte = 8 bits; each next unit is ×1024.

Real-world example: Closing a program without saving loses unsaved work because it lived in volatile RAM, not on the disk.

Example 1. Which memory is volatile (erased when power is off)?

• RAM.

Example 2. How many bits are in one byte?

• 8 bits.

Example 3. Arrange from smallest to largest: GB, KB, MB, TB.

• KB < MB < GB < TB.

Definition: An operating system (OS) is system software that manages the computer's hardware and software and provides an interface for the user.

What an OS Does

• Manages memory, processes, files and devices.
• Provides the user interface (desktop, windows, icons).
• Examples: Windows, macOS, Linux, Android.

Windows Basics

• Windows Explorer / File Explorer — manages files and folders.
• Keyboard shortcuts: Ctrl+C copy, Ctrl+V paste, Ctrl+X cut, Ctrl+Z undo, Ctrl+S save.
• The Recycle Bin temporarily holds deleted files.

Real-world example: When you copy a file with Ctrl+C and paste it elsewhere, the OS is managing that file operation for you.

Example 1. Which is an operating system: MS Word, Windows, Chrome, Excel?

• Windows.

Example 2. The shortcut Ctrl+Z is used to:

• Undo the last action.

Example 3. Deleted files in Windows are first moved to the:

• Recycle Bin.