Unit 2: Memory and I/O Devices

1. Memory: Concepts and Units

Computer memory is the storage space in the computer, where data is to be processed and instructions required for processing are stored. It is divided into a large number of small parts called cells.

Units of Memory

Data in a computer is stored in binary form (0s and 1s). The following table shows the standard units used to measure memory capacity:

2. Primary Memory: RAM and ROM

Primary memory holds only those data and instructions on which the computer is currently working. It has a limited capacity and data is lost when power is switched off (in the case of RAM).

RAM (Random Access Memory)

RAM is the internal memory of the CPU for storing data, programs, and program results. It is a read/write memory which stores data until the machine is working.

• Volatile: Data is lost when power is interrupted.
• Types:
  • SRAM (Static RAM): Faster and more expensive; used as cache.
  • DRAM (Dynamic RAM): Needs to be refreshed thousands of times per second; used as main memory.

ROM (Read Only Memory)

ROM is memory from which we can only read but cannot write on it. This type of memory is non-volatile. The information is stored permanently in such memories during manufacture.

• Non-volatile: Retains data even after the power is turned off.
• Usage: Stores the BIOS (Basic Input/Output System) to start the computer.
• Types: PROM (Programmable ROM), EPROM (Erasable Programmable ROM), and EEPROM (Electrically Erasable Programmable ROM).

3. Secondary Storage Devices

Secondary memory is also known as external memory or non-volatile memory. It is slower than main memory but used for storing data/information permanently.

HDD (Hard Disk Drive)

The standard main storage device for most computers. It uses magnetic storage to store and retrieve digital information using rapidly rotating disks (platters) coated with magnetic material.

SSD (Solid State Drive)

A newer, faster type of device that stores data on instantly-accessible memory chips. Unlike HDDs, SSDs have no moving parts, making them quieter and more durable.

Flash Drives

Small, portable storage devices that connect via a USB port. They use "flash" memory, which is a type of EEPROM.

Optical Disks: DVD

Digital Versatile Discs (DVD) are optical storage media that use laser technology to read and write data. They offer higher storage capacity than traditional CDs.

4. Input Devices

Input devices allow the user to send data or instructions to the computer.

• Keyboard: The most common input device used to enter text and commands.
• Mouse: A pointing device used to control a cursor on the screen.
• Scanner: A device that captures images from photographic prints, posters, magazine pages, and similar sources for computer editing and display.

5. Output Devices

Output devices translate the computer's processed data into a form that humans can understand.

LCDs (Liquid Crystal Displays)

The most common type of monitor used today. It uses the light-modulating properties of liquid crystals to display images.

Printers

Used to create "hard copies" of digital documents.

• Impact Printers: Use a striking mechanism (e.g., Dot Matrix).
• Non-Impact Printers: Do not hit the paper (e.g., Inkjet, Laser).

Plotters

A specialized output device used to produce high-quality vector graphics. They are commonly used by engineers and architects for technical drawings and blueprints.

6. Latest I/O Devices in the Market

The technology market is constantly evolving with newer peripheral devices:

• Touchscreens: Combine input and output functionality into a single interface.
• 3D Printers: Create physical 3D objects from digital files.
• Biometric Sensors: Input devices for security (fingerprint scanners, iris recognition).
• VR Headsets: High-end output devices for immersive virtual reality environments.

7. Exam Focus Corner