Recall — GCSE Flashcards
💻 GCSE Computer Science Flashcards
Algorithms, data, hardware and networks — 10 free revision cards. Study them below, or add the whole deck to Recall and let FSRS spaced repetition schedule your revision so it actually sticks.
Convert the denary number 156 to binary.
10011100
Workings: 156 = 128 + 16 + 8 + 4
| 128 | 64 | 32 | 16 | 8 | 4 | 2 | 1 |
|---|---|---|---|---|---|---|---|
| 1 | 0 | 0 | 1 | 1 | 1 | 0 | 0 |
Workings: 156 = 128 + 16 + 8 + 4
| 128 | 64 | 32 | 16 | 8 | 4 | 2 | 1 |
|---|---|---|---|---|---|---|---|
| 1 | 0 | 0 | 1 | 1 | 1 | 0 | 0 |
Convert the binary number 11010110 to denary.
214
128 + 64 + 16 + 4 + 2 = 214
128 + 64 + 16 + 4 + 2 = 214
What is the difference between RAM and ROM?
RAM (Random Access Memory): volatile, read/write, stores currently-running programs and data.
ROM (Read-Only Memory): non-volatile, read-only, stores boot firmware (BIOS).
ROM (Read-Only Memory): non-volatile, read-only, stores boot firmware (BIOS).
Compare linear search and binary search.
Linear search: check each item in turn. Works on unsorted lists. O(n).
Binary search: repeatedly halve a sorted list. O(log n). Much faster for large lists, but the list must be sorted first.
Binary search: repeatedly halve a sorted list. O(log n). Much faster for large lists, but the list must be sorted first.
Describe the bubble sort algorithm.
Repeatedly steps through the list, comparing adjacent pairs and swapping them if in the wrong order. Largest values "bubble" to the end.
Repeat until no swaps made in a pass. O(n²) — simple but inefficient.
Repeat until no swaps made in a pass. O(n²) — simple but inefficient.
What are the three programming constructs?
1. Sequence — code executed in order
2. Selection —
3. Iteration —
All algorithms can be built from these three.
2. Selection —
if/else decisions3. Iteration —
while/for loopsAll algorithms can be built from these three.
What is the CPU fetch-execute cycle?
1. Fetch instruction from memory (using Program Counter)
2. Decode the instruction
3. Execute the instruction
Repeats continuously. PC increments to point to the next instruction.
2. Decode the instruction
3. Execute the instruction
Repeats continuously. PC increments to point to the next instruction.
Compare TCP and UDP.
TCP (Transmission Control Protocol): connection-based, reliable, ordered, error-checked. Used for web, email.
UDP (User Datagram Protocol): connectionless, fast, no guarantees. Used for video streaming, gaming, DNS.
UDP (User Datagram Protocol): connectionless, fast, no guarantees. Used for video streaming, gaming, DNS.
What is hashing and where is it used?
A one-way function that maps data of any size to a fixed-size value (the hash).
Uses: password storage, data integrity (checksums), hash tables.
Good hashes: deterministic, fast, low collisions, irreversible.
Uses: password storage, data integrity (checksums), hash tables.
Good hashes: deterministic, fast, low collisions, irreversible.
What is the difference between high-level and low-level languages?
High-level (Python, Java): close to human language, easier to read/write, portable, must be compiled or interpreted.
Low-level (assembly, machine code): close to hardware, fast, processor-specific.
Low-level (assembly, machine code): close to hardware, fast, processor-specific.
These 10 cards are a free starter deck — a companion for memorising the core facts, not a complete course. In the Recall app you can also paste your own class notes and have AI build decks for the topics your exam board covers.