National Year 11 Computer Science

1. 3.4 Computer systems

3.4.1 Hardware and software · 3.4.2 Boolean logic · 3.4.3 Software classification · 3.4.4 Programming languages and translators · 3.4.5 Systems architecture

• Computers and Computing: Evolution, Parts and I/O Devices – A computer is an electronic machine that takes input, processes it under the control of a program, stores data and gives output. Computing devices grew from the abacus to smartphones. Every computer has an input unit, a CPU, memory and an output unit, joined by buses and ports.
• Boolean Logic – Boolean logic works with only two values: 1 (true) and 0 (false). Logic gates act on them: NOT flips a value; AND gives 1 only if all inputs are 1; OR gives 1 if any input is 1; NAND and NOR are the opposites of AND and OR; XOR gives 1 when inputs differ. A truth table lists the output for every input combination (2ⁿ rows for n inputs). De Morgan's laws: (A·B)' = A' + B' and (A + B)' = A'·B'. Gates joined together form logic circuits that match Boolean expressions.
• Software: System and Application, Generic and Specific – Software is a set of programs. System software (operating system, device drivers, utilities, language translators) runs and looks after the computer. Application software does a user's task. Application software can be generic (general-purpose, ready-made for many users) or specific-purpose (customised for one organisation's need).
• Programming Languages and Translators – A CPU can only run machine code: binary instructions. Low-level languages are machine code and assembly language (short mnemonics such as LOAD and ADD, one per machine instruction). High-level languages such as Python, Java and C are easier for people to read and write, and one line may become many machine instructions. Translators convert code: an assembler turns assembly into machine code; a compiler translates a whole high-level program into an executable before it runs; an interpreter translates and runs one line at a time. Some languages compile to bytecode, which a virtual machine then runs.
• Computer Architecture – Computer architecture is the design of how a computer's parts work together. Most computers follow the von Neumann model: a CPU and one main memory that stores both the program and its data, joined by the address, data and control buses. The CPU repeats the fetch-decode-execute cycle using special registers (PC, MAR, MDR, CIR, ACC), a control unit and an ALU. Speed depends on clock speed, number of cores and cache size. Instructions are machine code (binary); assembly gives them short names. Designs vary: Harvard (separate memories), RISC vs CISC, and small embedded systems.

2. 3.5 Fundamentals of computer networks

Network types and connections · Protocols and layers · Network security

• Computer Networks: Types, Devices and Topologies – A computer network is a group of devices connected to share data and resources. By area, networks are PAN, LAN, MAN and WAN. Devices do different jobs: a modem converts digital and analog signals, a repeater boosts a weak signal, a hub sends data to all ports, a switch sends it only to the right device, a router joins networks and chooses a path, and a gateway joins networks that use different protocols. Topology is the layout of connections: star, bus, tree and mesh, each with its own strengths and weaknesses.
• Network Protocols and the TCP/IP Model – A protocol is a set of rules that devices agree on so they can talk to each other. Networking is split into four layers (the TCP/IP model). The Application layer has protocols that apps use: HTTP and HTTPS for web pages, SMTP to send email and IMAP to read email kept on a server. The Transport layer (TCP) splits data into numbered packets, checks them and resends any that are lost. The Internet layer (IP) adds addresses and routes packets. The Link layer sends the bits over a cable (Ethernet) or by radio (Wi-Fi). Going down the stack each layer adds a header; going up on the other side each header is removed. Layers make networks easier to build and change, because each layer only needs to talk to the layer just above and below it.
• Cybersecurity: Threats and How We Stop Them – Cybersecurity protects computers, networks and data. It aims for confidentiality, integrity and availability (the CIA triad). Common threats are malware, phishing and social engineering, brute-force password attacks and denial of service. Defences include strong authentication, encryption, firewalls, anti-malware software, updates, access control and backups.

3. 3.6 Cyber security

3.6.1 Fundamentals of cyber security · 3.6.2 Cyber security threats · 3.6.3 Detecting and preventing threats

• Cybersecurity: Threats and How We Stop Them – Cybersecurity protects computers, networks and data. It aims for confidentiality, integrity and availability (the CIA triad). Common threats are malware, phishing and social engineering, brute-force password attacks and denial of service. Defences include strong authentication, encryption, firewalls, anti-malware software, updates, access control and backups.

4. 3.7 Relational databases and SQL

3.7.1 Relational databases · 3.7.2 SQL

• Database Concepts: DBMS, Relations and Keys – Keeping data in separate files causes duplication, inconsistency and poor security. A database stores related data in one organised place, and a DBMS (like MySQL) is the software that manages it. In the relational model, data is kept in tables (relations) made of columns (attributes) and rows (tuples); a domain is the set of allowed values of a column. A candidate key uniquely identifies each row; one is chosen as the primary key and the others are alternate keys.
• SQL with MySQL: Create Tables, Change Rows and Ask Questions – SQL (Structured Query Language) is the language used to talk to a relational DBMS like MySQL. DDL commands (CREATE, ALTER, DROP) define tables; DML commands (INSERT, UPDATE, DELETE) change rows; DQL (SELECT) reads data. Each column has a data type such as INT, FLOAT, CHAR, VARCHAR or DATE. SELECT … WHERE filters rows using relational operators, BETWEEN, AND/OR/NOT and IS NULL.

5. 3.8 Ethical, legal and environmental impacts

Impacts of digital technology on society

Coming soon