Introduction
Every computer, from a smartphone to a supercomputer, follows the same simple loop: it takes in data (input), works on that data inside the CPU and memory (processing), gives back results (output), and keeps data for later (storage). The devices that let a computer talk to the outside world and remember things are called peripheral devices or I/O and storage devices.
For BCS, Bank, and IT-officer exams this topic is a guaranteed scorer. Questions are usually direct and factual: "Which one is an input device?", "1 KB = how many bytes?", "Which memory is volatile?", "OMR is used for what?", "SSD vs HDD?". If you master the classifications and the number system of storage units, you can answer almost every question in seconds. This lesson builds the topic from first principles so you never have to guess.
Learning objectives
By the end of this lesson you will be able to:
- Explain the input-process-output-storage model of a computer.
- Classify any device as input, output, both (I/O), or storage.
- Name and describe the major input devices (keyboard, mouse, scanner, OMR, OCR, MICR, barcode, biometric, etc.) and what each is used for.
- Name and describe the major output devices (monitor, printer types, plotter, speaker, projector) and the difference between hardcopy and softcopy.
- Understand the memory hierarchy: registers, cache, RAM, ROM, secondary and tertiary storage.
- Distinguish volatile vs non-volatile, primary vs secondary, magnetic vs optical vs solid-state storage.
- Convert confidently between bit, byte, KB, MB, GB, TB and solve capacity/transfer-time problems step by step.
- Avoid the classic traps examiners set on this topic.