A Level Computer Science Flashcards

Flashcards covering key concepts from the A Level Computer Science course.

Why is compression needed in Data Transfer?

Compression is crucial for reducing file size to facilitate efficient data transfer over the Internet. Smaller files have faster transmission times and require less bandwidth consumption.

What are the benefits of Lossy compression?

Greatly reduced file sizes and suitable for media streaming where some data loss is acceptable.

What are the drawbacks of Lossy compression?

Irreversible loss of data quality and is not suitable for text or archival storage

What are the benefits of Lossless compression?

Maintains original data and best for text and data that requires integrity

What are the drawbacks of Lossless compression?

Larger file sizes than lossy and Requires high bandwidth when streaming

What is Run Length Encoding (RLE)?

A form of data compression that condenses identical elements into a single value with a count.

What is Dictionary Coding?

Replaces recurring sequences with shorter, unique codes. A 'dictionary' is compiled to map original sequences to special codes.

What is Encryption?

Converting readable data into an unreadable format to secure data from unauthorised access. Encryption methods use 'keys' to scramble or unscramble data.

How does Symmetric Encryption work?

The sender uses a key to encrypt the data before transmission, and the receiver uses the same key to decrypt the data.

How does Asymmetric Encryption work?

Uses two keys: a public key for encryption and a private key for decryption. Receivers share their public key, and senders use it to encrypt data. Only the receiver's private key can decrypt the data.

What is Hashing?

A method to convert any data into a fixed-size string of characters (a digest). The same input always produces the same hash, and even a minor change in input produces a radically different hash.

What are some common hashing algorithms?

MD5 (Message Digest 5), SHA-1 (Secure Hash Algorithm 1), SHA-256 (Part of the SHA-2 family), SHA-3

What is referential integrity?

Ensures consistency between related tables in a relational database by maintaining valid relationships between primary and foreign keys.

What is a Database Management System (DBMS)?

Software used to manage databases.

What is First Normal Form (1NF)?

Each column in a table must contain single, indivisible (atomic) values, no repeating groups, unique column names, and a unique identifier (primary key).

What is Second Normal Form (2NF)?

Must fulfill all 1NF requirements, only apply to tables with a compound primary key, have full functional dependency, and have no partial dependencies.

What is Third Normal Form (3NF)?

Must fulfill all 2NF requirements and have no transitive dependencies. Non-prime attributes must not depend on other non-prime attributes.

What is an entity?

Something worthy of capturing and storing data about (e.g., students, orders, products, courses, customers). Entities become tables in a relational database.

What is an entity relationship diagram (ERD)?

A diagram that represents the entities (tables) that will be in a database and the relationships between these entities.

What are the methods for Capturing Data?

Forms, OMR (Optical Mark Recognition), OCR (Optical Character Recognition), Sensors, Barcodes, Data mining

What is OMR (Optical Mark Recognition)?

Detects marked areas on paper by using a special machine to read the marks. Used for exams, surveys, lottery tickets to automate data collection and entry.

What is OCR (Optical Character Recognition)?

Converts printed or handwritten text into digital format, useful for digitising documents and assisting in searching and editing text.

What is Query By Example (QBE)?

A user-friendly method for constructing database queries using a visual interface, allowing users to search for data by providing an example of the desired output.

What are the benefits of APIs?

Encourages code reuse and modular programming, simplifies application development by providing pre-built functionalities, and facilitates seamless integration of different services.

What is SQL (Structured Query Language)?

A programming language used to interact with a DBMS. Allows a user to select data, insert data, delete records, and delete tables.

What is referential integrity?

Ensures consistency between related tables in a relational database. Maintains valid relationships between primary and foreign keys, and prevents orphaned records.

What is a transaction?

A sequence of database operations treated as a single unit of work, ensuring data consistency and integrity during simultaneous access.

What is ACID?

A set of rules (Atomicity, Consistency, Isolation, Durability) that all Database Management Systems (DBMS) must use to ensure data integrity and guarantee reliable processing of transactions.

What are Networks?

A set of interconnected devices (such as computers, printers, and servers) designed to share resources, exchange data, and communicate with each other.

What is protocol layering?

The way network protocols are divided into layers, each of which performs specific functions. This allows for modular design, simplifies troubleshooting, and promotes interoperability.

Name the 4 layers of TCP/IP models

Application, Transport, Internet and Link

What is TCP/IP?

Transmission Control Protocol/Internet Protocol, is a suite of communication protocols used to interconnect network devices on the internet

What is Packetizing?

A process where a large message is divided into smaller, manageable units called packets. Each packet can then be sent individually over the network.

What is Packet Switching?

A networking communication method that breaks down data into smaller packets and sends these packets separately along different routes, and then reassembles them at their destination.

What is Circuit Switching?

A communication method where a dedicated communication path is established between two devices for the duration of their conversation, and all packets are sent along the same route.

What is a DNS Resolver?

The first stop in the DNS lookup process, usually provided by your internet service provider (ISP).

Example of common internet Protocol

HTTP, HTTPS, SMTP, TCP, UDP and IP

What is a Modem?

A device that modulates an analogue carrier signal to encode digital information and also demodulates a carrier signal to decode the transmitted information. used for DSL, cable, or dial-up internet connections

What is a Router?

A network hardware device that routes data from a local area network (LAN) to another network connection. It joins two networks together.

What is NIC (Network Interface Card)?

A hardware component that enables a device to connect to a network. NICs have a built-in ethernet port and can be connected to a network via an ethernet cable

What is a Wireless Access Point (WAP)?

Acts as a central transmitter and receiver of Wi-Fi signals that connect to the wired network from a fixed location using Ethernet or Fibre optic cable and project a Wi-Fi signal to a designated area

What is a Hub?

A networking device which is used to connect multiple devices in a network . Hubs are dumb which means it sends all infromation to all conections.

What is a Switch?

A network switch is a networking device that connects devices on a computer network and uses packet switching to receive, process and forward data to the destination device. Only sends data to the intended source via look up tables of MAC addresses

What are the Common Network Threats?

Hackers, Viruses, Malware, Denial of Service (DoS), SQL Injection, Phishing, Pharming and Social Engineering

What is client side processing?

Involves carrying out code or processing tasks on the user's device, usually within the web browser, instead of on the server. Client side processing is primarily done using JavaScript using DOM manipulation and AJAX

What is server side processing?

Involves running code and carrying out operations on the server instead of on the client's device or browser using PHP, Python, Ruby, or Java to handle incoming requests, process data, interact with databases, and generate dynamic content

What is Search Engine Crawling?

Web pages are discovered by search engines through software programs called crawlers that follow links from one webpage to another, systematically visiting pages on the web.

What is Search Engine Indexing?

The data extracted from the webpage is indexed, which involves storing the collected information in a structured manner within a search engine's database. Each word is included in the index as an entry, along with its position on the page

What does LAN stand for?

Local Area Network

What does WAN stand for?

Wide Area Network

Name four key elements of the PageRank algorithm

Link analysis, Link weight distribution, Iterative calculation and Damping factor