Exchanging Data Quiz

Lossy compression reduces file size by permanently removing some data, resulting in a loss of quality. It is commonly used for media files such as images and audio where perfect accuracy is not essential. Lossless compression reduces file size without losing any data, allowing the original file to be perfectly reconstructed. It is used for text and data files where accuracy is critical. 

Run Length Encoding (RLE) compresses data by replacing sequences of repeated values with a single value and a count, making it efficient for data with many repeated elements. Dictionary coding replaces repeated patterns with shorter codes stored in a dictionary, allowing recurring sequences to be represented more efficiently. 

Symmetric encryption uses a single key for both encryption and decryption, making it fast and suitable for large data volumes, but it requires secure key distribution. Asymmetric encryption uses a public and private key pair, providing greater security for communication, although it is slower and more computationally intensive. 

Hashing converts data into a fixed-length value, which represents the original data. It is used for securely storing passwords, verifying data integrity by comparing hashes, and improving search efficiency through hash tables. 

A relational database organises data into tables with rows and columns. A primary key uniquely identifies each record. A foreign key links one table to another by referencing a primary key. A secondary key is used for searching but does not uniquely identify records. 

Flat file databases store all data in a single table, which can lead to redundancy and anomalies. Relational databases use multiple related tables, reducing redundancy and improving data integrity through structured relationships. 

Normalisation is the process of organising a database to reduce redundancy. First Normal Form requires atomic data and no repeating groups. Second Normal Form removes partial dependencies on composite keys. Third Normal Form removes transitive dependencies, ensuring all non-key attributes depend only on the primary key. 

Indexing creates a data structure that allows faster searching of records. It improves query performance by reducing the amount of data that must be scanned, although it may increase storage requirements. 

SQL is used to interact with databases. SELECT retrieves data, INSERT adds new records, UPDATE modifies existing data, and DELETE removes records. These commands allow efficient data manipulation and retrieval. 

Referential integrity ensures that relationships between tables remain consistent. Foreign keys must match existing primary keys, preventing invalid or orphaned records and maintaining data accuracy. 

ACID properties ensure reliable transaction processing. Atomicity ensures transactions are all-or-nothing. Consistency ensures valid database states. Isolation prevents interference between transactions. Durability ensures completed transactions are permanently stored. 

Packet switching divides data into packets that travel independently across a network and are reassembled at the destination, improving efficiency and reliability. Circuit switching establishes a dedicated communication path, which remains reserved for the duration of the transmission, but can be inefficient. 

The TCP/IP stack consists of four layers. The application layer handles user-level protocols, the transport layer ensures reliable communication, the network layer manages addressing and routing, and the link layer handles physical transmission of data. 

Client-server networks use a central server to manage resources and provide services to clients, offering better security and control. Peer-to-peer networks allow devices to share resources directly without a central server, making them simpler but less secure and harder to manage. 

Client-side processing occurs in the user’s browser, providing faster interaction and reducing server load. Server-side processing occurs on the web server, handling tasks such as database queries and authentication, ensuring security and centralised control.