Cameroon GCE A-Level Computer Science - independent foundations cheat sheet
Cameroon GCE A-Level Computer Science - independent foundations · Keep the key ideas within reach.
Programming and Software Development
Recursion needs a base case and progress toward that base case.
Overloading uses different signatures; overriding replaces an inherited method.
Unit tests isolate units; integration tests combine them.
Short-circuit evaluation can skip the right operand.
Pass-by-value copies arguments; pass-by-reference can mutate the caller's object.
Computational Thinking and Problem Solving
Decomposition breaks problems down; abstraction removes irrelevant detail.
Binary search requires sorted data and is O(log n).
Merge sort is O(n log n) worst case; bubble sort is O(n^2).
Trace tables prevent guessing about loop output.
Update search bounds to mid + 1 or mid - 1, not mid.
Computing Systems
Fetch-decode-execute uses the PC, IR, ALU, and registers.
Memory hierarchy: registers, cache, RAM, storage, offline.
RAM is volatile; SSDs retain data without power.
A process has its own address space; threads share one.
Authentication verifies identity; authorization grants permissions.
TCP is reliable and connection-oriented; UDP is connectionless and lower overhead.
IP addresses route between networks; MAC addresses work on the local link.
A /26 subnet has 64 addresses and 62 usable hosts.
DNS resolves names; DHCP assigns addresses.
Security protects data; privacy governs collection and use.
Data, Databases, and Information Retrieval
Primary keys are unique and non-null; foreign keys enforce referential integrity.
WHERE filters rows before grouping; HAVING filters aggregated groups.
COUNT(*) counts rows; COUNT(column) skips NULL values.
LEFT JOIN preserves unmatched left rows; INNER JOIN removes them.
Precision = relevant retrieved / retrieved; recall = relevant retrieved / all relevant.
Impacts of Computing
The digital divide includes access, affordability, skills, and broadband quality.
Automation can displace some jobs while creating or reshaping others.
Algorithmic bias can arise from biased data, design, or deployment context.
Impact analysis asks who benefits, who pays, who is excluded, and what is assumed.
Adoption is uneven; access alone does not guarantee equitable outcomes.
CIA triad: confidentiality, integrity, and availability.
Authentication proves identity; authorization grants permissions.
Encryption is reversible with a key; hashing is one-way.
Use unique salts and slow password hashing, never plain encryption, for passwords.
Least privilege and defense in depth reduce the impact of failures.