Notes: Database, Computer Network & Communication | Information and Communication Technology (ICT) for UGC NET PDF Download

Database

It is a collection of logically related information in an organized way so that it can be easily accessed, managed, and updated. A database comprises inter-related records that facilitate adding, updating, and deleting data.

Components of a Database

1. Tables: These serve as the building blocks or relations in any relational database model, where all the actual data is defined and entered.

• Field: An area within a record designated for a specific piece of data, such as customer number, name, address, etc. It is also referred to as a 'column'.
• Record: A collection of data items from all fields related to one entity like a person, company, or transaction. It's also known as a 'row' or a 'tuple'.

2. Queries:

Queries are essentially questions that are based on the available data within a database. They consist of specific instructions that indicate the fields, records, and summaries that a user desires to retrieve from the database.

3. Forms:

Forms, akin to tables, serve the purpose of both viewing and editing data. However, forms are primarily utilized for viewing data within an underlying table on a record-by-record basis.

4. Reports:

Reports are essential when there is a need to print the records that have been retrieved from a database. Designing a report becomes necessary in such instances.

Data Hierarchy

• It involves the structured organization of data, typically in a hierarchical manner.

Starting from the top level downwards, the hierarchy is as follows:

• Database
• Comprising multiple files
• Containing various records
• Consisting of different fields
• Which are further broken down into bytes (characters)
• Composed of bits

Computer Network

Communication media in a network refers to the transmission or connecting media utilized within the network. These can be categorized into two main types:

1. Guided Media or Wired Technologies

Guided media are characterized by the use of physical cabling systems that guide data signals along specific paths. Examples of guided media include:

• Ethernet Cable: Commonly used for local area networks (LANs) to connect devices within a limited area.
• Coaxial Cable: Utilized in cable television networks and broadband internet connections for transmitting high-frequency signals.
• Fiber Optic Cable: Employs thin strands of glass or plastic to transmit data signals using light pulses, offering high-speed and long-distance transmission capabilities.

2. Unguided Media or Wireless Technologies

Unguided media involve the transmission of information over distances without the use of physical wires or conductors. Examples of unguided media include:

• Radiowave: Utilized in radio communication systems for broadcasting and wireless networking.
• Microwave: Employed in microwave communication systems for point-to-point transmission over short to medium distances.
• Satellite: Utilized for long-distance communication, particularly in remote areas where terrestrial infrastructure is unavailable or impractical.
• Infrared Wave: Used in wireless communication technologies like infrared data association (IrDA) for short-range data transmission between devices.
• Bluetooth: A short-range wireless technology commonly used for connecting peripherals such as keyboards, mice, and headphones to computers and mobile devices.

Guided media, such as ethernet, coaxial, and fiber optic cables, provide reliable and high-speed data transmission over specific paths, making them suitable for wired networks within buildings or campuses.

On the other hand, unguided media, including radiowaves, microwaves, and satellites, offer flexibility and mobility, enabling wireless communication over long distances or in situations where laying physical cables is impractical.

Both guided and unguided media play crucial roles in modern communication networks, with each offering distinct advantages and applications based on factors such as cost, speed, distance, and mobility requirements.