Computer Hardware: Input, Output, CPU and Memory Explained

Input devices

Device	Function	Where it is used
MICR	Reads magnetic-ink characters	Bank cheque clearing
OCR	Converts printed text into editable text	Scanned letters into a document
OMR	Detects marks in fixed positions	Examination answer sheets
Barcode reader	Reads barcodes	Library books, stores inventory
Biometric scanner	Captures fingerprint, face or iris	Staff attendance

Key point

MICR is for cheques, OCR is for recognising characters, and OMR is for detecting bubbles or marks. These three are interchanged in almost every exam.

Output devices

Impact printer: physically strikes the paper, such as a dot-matrix printer.
Non-impact printer: prints without striking, such as inkjet and laser printers.
Plotter: produces large, precise drawings such as campus plans.
Touchscreen: acts as both an input and an output device.

The CPU

The Central Processing Unit is often called the brain of the computer. It has three parts:

ALU (Arithmetic Logic Unit): performs arithmetic and logical operations.
CU (Control Unit): controls and coordinates all operations.
Registers: very fast temporary storage inside the CPU.

Memory

Primary memory

RAM: volatile, so its contents are lost when power goes off.
ROM: non-volatile. Its types are PROM, EPROM and EEPROM.
Cache: very fast memory between the CPU and RAM.

Secondary storage

HDD, SSD, pen drives and optical discs. All of these are non-volatile. An SSD uses flash memory and has no moving parts, while an HDD has spinning platters.

Memory hierarchy

Speed and cost fall from left to right. Capacity rises from left to right.

Example

An unsaved document sits in RAM. Because RAM is volatile, a sudden power cut erases it. Once saved, it moves to secondary storage and survives.

Exam tip

In speed-order questions, fix the two ends first: Register is always fastest and tape or optical disc is always slowest. That usually removes two or three options at once.

Computer Hardware: Input, Output, CPU and Memory

Key points