Input, Output and Storage Devices

Input Devices

An input device is any hardware used to enter data and instructions into a computer. It converts the user's actions or real-world data into a form the computer can process. Common input devices include:

• Keyboard — used to type text, numbers, and commands.
• Mouse — a pointing device used to select, click, and move items on the screen.
• Scanner — converts a printed document or photograph into a digital image that the computer can store.
• Microphone — captures sound and voice as digital audio.
• Webcam — captures live video and images.
• Barcode reader — reads the barcode printed on products (widely used at shop billing counters).
• Touch screen — acts as both an input and an output device, letting the user give commands by touching the display directly (as on a smartphone or an ATM).

Output Devices

An output device is any hardware that presents the processed results (information) to the user, either on screen, on paper, or as sound. Common output devices include:

• Monitor (VDU — Visual Display Unit) — displays output on a screen; this is called soft copy because it is temporary and disappears when the screen changes or the computer is switched off.
• Printer — produces output on paper; this is called hard copy because it is permanent and physical.
• Speakers / headphones — produce sound output.
• Projector — displays the computer's screen output on a large surface for a group to view.

Storage Devices

Memory and storage let a computer keep data and instructions. There are two broad kinds:

Primary memory (main memory): directly accessible by the CPU, fast, and used for data currently being worked on. Its two main types are:

• RAM (Random Access Memory) — temporary, read/write memory that holds the data and programs currently in use. It is volatile, meaning its contents are lost when the computer is switched off.
• ROM (Read Only Memory) — permanent memory that stores essential start-up instructions built in by the manufacturer. It is non-volatile, meaning its contents are retained even when the power is off, and normally it can only be read, not changed by the user.

Secondary storage (auxiliary storage): used to store data and programs permanently for future use. It is non-volatile, has a much larger capacity than primary memory, and is cheaper per unit of storage, but is slower to access. Common examples include:

• Hard Disk Drive (HDD) — the main permanent storage inside most computers, offering large capacity.
• Solid State Drive (SSD) — a faster, chip-based form of permanent storage with no moving parts.
• Pen drive / USB flash drive — a small, portable device for carrying data between computers.
• Memory card — compact removable storage used in phones and cameras.
• Optical discs (CD/DVD) — discs read using a laser, used for storing or distributing data (less common today).

Units of Storage …