Germany Jahrgangsstufe 12 Computer Science
Chapters: 7
1. Recursion
Recursion
- Recursion: Functions That Call Themselves – Recursion is when a function solves a problem by calling itself on a smaller version of the same problem. Every recursive function needs a base case, where it stops and returns an answer directly, and a recursive case that moves closer to the base case. Each call gets its own stack frame on the call stack; frames are removed as calls return.
2. Lists
Linked lists
- Linked Lists – A linked list stores items in nodes. Each node holds data and a pointer (the address of the next node). A variable called head points to the first node; the last node points to NULL. Nodes can sit anywhere in memory, so adding or removing at the front takes only a pointer change, but finding the k-th item means walking from the head.
3. Trees
Trees and binary search trees
- Trees in Data Structures: Binary Trees and Binary Search Trees – A tree stores data in nodes joined by edges, like a family tree turned upside down. The top node is the root, nodes with no children are leaves. A tree with n nodes has n − 1 edges. Depth of a node is its distance (in edges) from the root; height of the tree is the longest root-to-leaf path. In a binary tree every node has at most two children. A binary search tree (BST) keeps smaller keys on the left and bigger keys on the right, so searching skips half the tree at each step. Traversals visit every node: pre-order (root, left, right), in-order (left, root, right) and post-order (left, right, root). In-order on a BST gives sorted output.
4. How a computer works
How a computer works
- Basic Computer Organisation – A computer system has hardware (parts you can touch) and software (instructions). Input devices bring data in, the CPU (ALU + Control Unit + registers) processes it, and output devices give results. Memory forms a ladder: registers and cache are tiny and fastest, primary memory (RAM, ROM) holds running programs, and secondary storage (HDD, SSD, pen drive) keeps data permanently. Memory is measured in bits and bytes: 8 bits = 1 byte, and each bigger unit (KB, MB, GB, TB, PB) is 1024 times the one before.
5. Operating systems, processes and concurrency
Operating systems, processes and concurrency
- Operating System – An operating system (OS) is the main system software that sits between the user and the hardware and manages all resources. Its functions: process management (sharing the CPU between programs), memory management (giving and taking back RAM), file management, device management (through drivers) and security (passwords, permissions). Users talk to the OS through a user interface: command line (CLI), graphical (GUI), touch, voice or gesture. Examples: Windows, Linux, macOS, Android, iOS.
6. Information security
Information security
- 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.
7. Practical software development project
Software engineering project
- Software Development: From Idea to Working App – Good software is built in stages: analyse the problem and write requirements, design the solution, code it in small parts, test it with normal, boundary and erroneous data, deploy it to users and maintain it. Waterfall does each stage once in order; agile repeats short cycles. Robust programs validate input, and teams use version control, clear roles and feedback from users.