IB Digital Society SL cheat sheet

Core system model: input → processing → output → storage, with feedback loops that let the system adjust behaviour based on its own output.

Binary capacity rule: n bits encode 2^n distinct values; 1 byte = 8 bits = 256 values; ASCII uses 7 bits, Unicode code points require up to 21 bits.

Abstraction hierarchy: hardware → operating system → application → interface. Each layer hides lower-level complexity and exposes only a defined interface to the layer above.

TCP/IP has four layers (link, internet, transport, application). TCP is connection-oriented and reliable with retransmission; UDP is connectionless, lower-latency and does not guarantee delivery.

Bandwidth is maximum capacity in bits per second; latency is delay in milliseconds; throughput is the achieved rate and is capped by both, plus overheads, congestion and errors.

Lossless compression reconstructs the original data exactly (PNG, ZIP, FLAC); lossy compression permanently discards detail (JPEG, MP3) and degrades further with each re-encode.

CIA triad mapping: confidentiality → encryption and access control; integrity → hashing and checksums; availability → redundancy, failover and tested backups.

Symmetric encryption uses one shared key and is fast, suited to bulk data (AES); asymmetric encryption uses a public/private key pair and solves key distribution and enables digital signatures; TLS uses both.

Scaling rule: vertical scaling adds CPU/RAM to one machine and hits a ceiling; horizontal scaling adds machines and requires stateless services, load balancing and shared or replicated data stores.

Digital divide has three levels: access (devices and connectivity), skills and usage (literacy, confidence), and outcomes (benefits actually gained). Closing access alone does not close the gap.

Data protection principles: lawfulness and fairness, purpose limitation, data minimisation, accuracy, storage limitation, integrity and confidentiality, and accountability of the controller.

Stakeholder analysis rule: for each group record what they gain or lose, their power to affect the outcome, and their interest - high power plus high interest means engage closely, not inform.

Ethical lenses for a single dilemma: utilitarian (greatest net benefit), deontological (duties and rights breached or upheld), virtue (what a person of good character would do), justice (fair distribution of benefit and harm).

Misinformation is false content shared without intent to deceive; disinformation is false content created and circulated deliberately. The intervention differs: correction versus detection and platform enforcement.

Filter bubbles are caused by algorithmic personalisation ranking for engagement; echo chambers are caused by social homophily and group polarisation. Both narrow exposure but require different remedies.

Intellectual property: copyright is automatic and lasts roughly life plus 50–70 years; patents require novelty and last about 20 years; trademarks protect brand identity; open licences (CC, GPL) use copyright to grant permissions rather than remove it.

Net neutrality is the principle that ISPs do not block, throttle or sell priority for specific traffic; without it, paid prioritisation and zero-rating favour established platforms over new entrants.

E-waste is among the fastest-growing waste streams; circular strategies - modularity, repairability, take-back schemes, certified recycling - reduce lifecycle impact, while data centres add significant electricity and water demand.

Incremental innovation improves an existing product or process; radical innovation creates a new category; disruptive innovation starts cheaper or simpler in low-end or non-consumer markets and improves until it displaces incumbents.

Design thinking cycle: empathise → define → ideate → prototype → test. It is iterative, so teams return to earlier stages as test evidence appears; it is not a one-pass waterfall.

Minimum viable product rule: build the smallest thing that tests the riskiest assumption, and define the success threshold before building, otherwise evidence cannot disconfirm the idea.

Feasibility screen (TELOS): technical, economic, legal, ethical, operational, schedule. A solution failing any single dimension is not viable regardless of the strength of the others.

Rogers' diffusion of innovations: innovators ≈2.5%, early adopters ≈13.5%, early majority ≈34%, late majority ≈34%, laggards ≈16%. Adoption over time follows an S-curve, with the steepest growth between early adopters and early majority.

Hype cycle stages in order: technology trigger → peak of inflated expectations → trough of disillusionment → slope of enlightenment → plateau of productivity.

Lock-in arises from switching costs in data, skills, integrations and contracts; interoperability standards and data portability rules are the standard countermeasures.

Prototype fidelity rule: low fidelity (paper, wireframe) for testing concept, flow and information architecture; high fidelity for interaction detail, visual design and micro-usability. Match fidelity to the question being tested.

Usability testing: observe representative users performing realistic tasks and record failures rather than opinions; about five users typically surface the majority of major usability problems.