Electronic-card Reader

I/O Devices Overview

• Serve as communication links between a computer and the external environment.
• Known as peripheral devices, they exist outside the CPU and memory of a computer.
• Input devices transfer data from external sources into primary storage.
• Output devices deliver processed information from primary storage to users.

Commonly Used Input Devices

• Keyboard Devices: Main method for data entry; the QWERTY layout is the most widely used.
• Point-and-Draw Devices: Facilitate quick selection on a GUI, including mouse, trackball, joystick, light pen, and touch screen.
• Data Scanning Devices: Capture images and convert them into digital formats for editing and storage.
• Speech Recognition Devices: Allow data input through voice, useful for hands-free operation or for individuals with disabilities.
• Vision-Based Devices: Enable input via visual recognition of objects.

Types of Input Devices Explained

• Mouse: Most popular pointing device, enabling document digitization.
• Optical Character Recognition (OCR): Converts scanned text images into editable ASCII codes, making document handling efficient.
• Optical Mark Reader (OMR): Detects marks made by pen/pencil, facilitating the grading of forms like tests.
• Bar-Code Reader: Decodes barcoded data using laser beams to interpret the alphanumeric information.

Commonly Used Output Devices

• Dot-Matrix Printers: Slow printers that use a matrix of pins to create characters, cost-effective but with lower quality.
• Inkjet Printers: Print with tiny ink jets, capable of producing images and different characters, more expensive and slower than dot-matrix printers.
• Drum Printers: Utilize a cylindrical drum with embossed characters for printing.

Data Communications Overview

• Sender: Originates and transmits a message.
• Medium: The channel carrying the message.
• Receiver: The entity that receives the message.

Data Transmission Modes

• Simplex: One-way communication (Sender to Receiver).
• Half-duplex: Alternating two-way communication (Sender <-> Receiver).
• Full-duplex: Simultaneous two-way communication (both Sender and Receiver).

Data Transmission Speed

• Bandwidth: Represents the data transmission rate; higher bandwidth allows more data transfer.
• Baud: Measures data transfer speed in bits per second (bps).

Categories of Data Transmission

• Narrowband: Low-speed channels, 45-300 baud, used mainly for telegraphy.
• Voiceband: Supports up to 9600 baud, typical for telephone communications.
• Broadband: High-speed channels, up to 1 million baud, enabling fast computer communications.

Data Transmission Media

• Twisted-pair Wire (UTP): Commonly used for networking.
• Coaxial Cable: Used for video and broadband signal transmission.
• Microwave System: Utilizes microwave signals for data transmission.
• Optical Fibers: Provide high-speed data transfer with low loss.

Network Topologies

• Star Network: Nodes are connected to a central hub.
• Ring Network: Each node connects to two others, forming a continuous loop.
• Bus Network: All nodes share a single communication line.
• Hybrid Network: Combination of different topologies.

Types of Networks

• Local Area Network (LAN): Limited geographic range, high speed, fewer errors, and lower costs.
• Wide Area Network (WAN): Covers a larger area with extended communication capabilities.
• Metropolitan Area Network (MAN): Shares features of both LANs and WANs.

Network Interface Card (NIC)

• Hardware that connects a computer to a network physically and functionally.
• Provides a port for network cable attachment.

Internetworking

• The process of connecting multiple networks into a single cohesive system.
• Aims to create a uniform network experience, hiding underlying complexities.
• Utilizes devices like bridges, routers, and gateways, with the Internet as a prime example.