CSEC Information Technology - independent foundations cheat sheet
CSEC Information Technology - 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.
Computer architecture, logic and data representation
State whether addresses refer to bytes or words before calculating capacity.
Distinguish PC, instruction register, address register and data register.
For n-bit two’s complement the range is−2^(n−1) through 2^(n−1)−1.
Cache locality and pipeline hazards matter more than a clock-rate label alone.
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.
Office and Technology Applications
Relative references shift when copied; absolute references use $ to stay fixed.
Formulas recalculate from precedent cells; pasted values do not.
Mail merge needs a main document and a data source with matching field names.
PDF targets fixed-layout distribution; editable source structure is generally maintained more conveniently in the authoring format.
Chart choice follows the question: trend, comparison, or composition.
Share files with least privilege and version control.
Web structure, presentation, scripting and publishing
HTML structure, CSS presentation and JavaScript behavior have different roles.
Semantic controls and keyboard operation matter to accessibility.
Client validation does not replace trusted-server authorization and validation.
CMS permissions, review and publishing are separate decisions.
Uncompressed image arithmetic needs explicit dimensions, channels and overhead assumptions.
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.
Data representation, arrays, lists, trees and graphs
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).