A-Level Computer Science · Topic 1
Data structures, algorithms and complexity: every key term you need (+ practice quiz)
16 flashcard terms for A-Level Computer Science Topic 1, written to match the course framework. Study them here, then drill them as interactive flashcards, or test yourself with the 8-question quiz — free, no account needed.
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Abstraction Hiding unnecessary detail so a problem can be reasoned about at the right level. The idea underpinning both data types and program design.
Big O notation Describes how running time or space grows with input size in the worst case, ignoring constants and lower-order terms.
Binary search Repeatedly halves a sorted list, giving logarithmic time. Requires the data to be sorted first, unlike linear search.
Merge sort Divide and conquer: split until single elements, then merge sorted sublists. Consistently n log n but needs extra memory.
Bubble sort Repeatedly swaps adjacent out-of-order elements. Simple to implement but quadratic, so unusable on large datasets.
Stack Last in, first out. Used for call frames, undo history and converting or evaluating expressions in reverse Polish notation.
Queue First in, first out. A circular queue reuses freed space at the front by wrapping the rear pointer around the array.
Linked list Nodes each holding data and a pointer to the next. Insertion and deletion are cheap, but access is sequential rather than indexed.
Hash table Maps a key to an index using a hash function, giving near constant-time lookup. Collisions are resolved by chaining or probing.
Binary search tree Left child smaller, right child larger. Search is logarithmic when balanced but degrades to linear when the tree becomes a chain.
Graph traversal Breadth-first uses a queue and finds the fewest edges; depth-first uses a stack or recursion and explores one branch fully first.
Dijkstra's algorithm Finds the shortest path from one node to all others in a weighted graph with non-negative weights, using a priority queue.
Recursion A routine that calls itself, needing a base case to terminate. Elegant for tree and divide-and-conquer problems, but consumes stack space.
Fetch-decode-execute cycle The processor fetches the next instruction using the program counter, decodes it, then executes it — repeating for every instruction.
Two's complement Represents signed integers by negating and adding one, so a single adder circuit handles both addition and subtraction.
Normalisation Organising relational data to remove redundancy and update anomalies. Third normal form removes non-key dependencies.
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