Saarland Vocational Informatics, basic level - independent 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.

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.

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.

A process is defined by trigger, inputs, activities, decisions, controls and outputs, and usually crosses departmental boundaries.

Core processes touch the customer; support processes enable them, and both need owners and measures.

Parallel gateways run all paths; exclusive gateways select one path based on a condition.

Value stream maps expose queues and handoffs, which dominate lead time in most administrative processes.

Controls such as three-way match and segregation of duties improve assurance but add cycle time.

Prioritise improvement using the value-added ratio rather than the effort spent on individual tasks.

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.

Privacy includes purpose and proportionality, not secrecy alone.

GDPR principles apply within the regulation scope and are distinct obligations.

Consent is not the only possible lawful basis.

Domestic Ghanaian rules are not inferred from EU or US examples.

Access, permission, licensing and ethical judgment are different questions.

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.

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).