GACE Computer Science - independent content foundations cheat sheet

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.

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.

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.

n-bit two's complement range is −2^(n−1) to 2^(n−1) − 1; negation is invert then add 1.

Normalised two's complement mantissa has differing top two bits: 01… for positive, 10… for negative.

Longer mantissa = more precision; longer exponent = more range.

Bitmap size = width × height × colour depth ÷ 8; sound size = rate × resolution × channels × seconds ÷ 8.

Stacks are LIFO, queues FIFO; hash tables give near-constant lookup; linked lists give O(1) insertion once positioned.

Lossless compression preserves all data (RLE, Huffman); lossy discards detail permanently (JPEG, MP3).

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.