STPM ICT 958 cheat sheet

Digital divide: gap between those with reliable access to ICT and skills to use it, and those without; measured by access, affordability, literacy, and quality of connection.

Teleworking reduces commuting cost and office overhead but shifts responsibility for equipment, security, and work-life boundaries onto the employee.

E-government stages (Cresswell typology): information publishing, two-way interaction, transaction, integration, and participation.

Moore's Law: transistor count per integrated circuit roughly doubles every two years; it is an observation of a trend, not a physical law.

Green ICT has two aspects: greening of ICT (energy-efficient devices, data-centre PUE reduction) and greening by ICT (dematerialisation, smart grids, telepresence).

Digital signature legal effect depends on the governing statute (e.g. Malaysia's Digital Signature Act 1997 recognises licensed certification authorities); a scanned signature image alone is not a digital signature.

Automation displaces routine cognitive and manual tasks first; tasks requiring judgement, social interaction, and physical dexterity resist automation longer.

ICT4D projects fail most often from lack of local ownership, maintenance capacity, and electricity or connectivity, not from hardware cost alone.

Intellectual property types: copyright protects expression not ideas; patents protect novel, non-obvious, industrially applicable inventions for a limited term; trademarks protect source identifiers.

CPU cycle: fetch, decode, execute, write-back; the program counter holds the next instruction address and the instruction register holds the current instruction.

Pipelining overlaps instruction stages to raise throughput; hazards are structural (resource conflict), data (dependency), and control (branch).

Memory hierarchy from fastest/smallest to slowest/largest: registers, cache (L1/L2/L3), main memory, secondary storage; locality of reference makes caching effective.

Two's complement: negate by inverting all bits and adding 1; an n-bit signed range is -2^(n-1) to 2^(n-1)-1.

Karnaugh maps and Boolean identities (De Morgan: NOT(A AND B) = NOT A OR NOT B) simplify combinational logic before implementation.

RISC favours fixed-length instructions, many registers, and load-store architecture; CISC favours variable-length instructions and complex memory operands.

Amdahl's Law: speedup = 1 / ((1 - p) + p/s), where p is the parallelisable fraction and s the speedup of that fraction.

Virtual memory maps logical addresses to physical frames via page tables; a page fault triggers a disk fetch and possible replacement by LRU or FIFO.

Interrupts suspend the current process, save context, run the handler, and restore state; polling instead repeatedly tests device status.

Relational model terms: relation = table, tuple = row, attribute = column, degree = number of attributes, cardinality = number of tuples.

Primary key uniquely identifies a tuple and cannot be null; a foreign key references a primary key in another relation and enforces referential integrity.

Normalisation: 1NF removes repeating groups; 2NF removes partial dependencies on part of a composite key; 3NF removes transitive dependencies on non-key attributes.

SQL clause evaluation order: FROM, WHERE, GROUP BY, HAVING, SELECT, ORDER BY; HAVING filters groups, WHERE filters rows.

INNER JOIN returns matching rows only; LEFT JOIN keeps all left rows with nulls where unmatched; CROSS JOIN produces the Cartesian product.

ACID: Atomicity (all or nothing), Consistency (valid state to valid state), Isolation (concurrent transactions do not interfere), Durability (committed changes survive failure).

Entity-relationship cardinality 1:1, 1:M, M:N; an M:N relationship becomes a junction table with two foreign keys.

A DBMS provides concurrency control (locking or timestamping), recovery via logs, authorisation, and physical data independence.

Data warehouse vs operational database: warehouses are subject-oriented, integrated, time-variant, non-volatile, and optimised for analytical queries.

Program development stages: problem analysis, algorithm design, coding, testing and debugging, documentation, and maintenance.

Iteration types: definite (for loop, known count) versus indefinite (while/do-while, condition-driven); do-while guarantees at least one execution.

Pass by value copies the argument; pass by reference passes the address so the callee can modify the caller's variable.

Recursion needs a base case and a recursive case that moves toward it; each call consumes stack space, so deep recursion risks overflow.

Search complexity: linear search O(n) on unsorted data; binary search O(log n) but requires sorted data.

Sort complexity: bubble/selection/insertion O(n^2); merge sort O(n log n) with O(n) extra space; quicksort average O(n log n), worst O(n^2).

Trace tables record variable values after each statement to verify logic by hand; dry runs catch off-by-one and boundary errors before execution.

Structured constructs are sequence, selection, and iteration; a flowchart uses terminal, process, decision, input/output, and connector symbols.

Test data types: normal (valid expected), boundary (edges of valid range), and invalid/erroneous (must be rejected); black-box tests behaviour, white-box tests code paths.

OSI seven layers: Physical, Data Link, Network, Transport, Session, Presentation, Application; TCP/IP collapses these to Network Access, Internet, Transport, Application.

Encapsulation adds a header at each layer downward; de-encapsulation strips headers upward at the receiver.

IPv4 addresses are 32-bit; a /24 prefix leaves 8 host bits giving 254 usable hosts after removing network and broadcast addresses.

Private IPv4 ranges: 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16; NAT translates them to a public address.

TCP is connection-oriented with handshake, sequencing, acknowledgements, and retransmission; UDP is connectionless with no delivery guarantee, suited to streaming and DNS queries.

DNS resolves names to IP addresses hierarchically (root, TLD, authoritative); DHCP assigns addresses dynamically via DORA (Discover, Offer, Request, Acknowledge).

Switching vs routing: switches forward frames by MAC within a LAN; routers forward packets by IP between networks.

Transmission media: twisted pair (cheap, crosstalk-limited), coaxial, fibre (high bandwidth, immune to EMI), and wireless (subject to interference and attenuation).

Topologies: star is easy to fault-isolate but depends on the central device; mesh gives redundancy at high cabling cost; bus suffers collision and single-point cable failure.

Colour models: RGB additive for screens, CMYK subtractive for print; 24-bit true colour gives 2^24 = 16,777,216 colours.

Raster images store pixels and lose quality when enlarged; vector images store geometric primitives and scale without loss.

File size of uncompressed raster = width x height x colour depth in bits; halving either dimension quarters the pixel count.

Lossy compression (JPEG, MP3) discards perceptual detail; lossless (PNG, GIF, FLAC) preserves exact data.

HTML structure vs CSS presentation vs JavaScript behaviour; separating them improves maintainability and accessibility.

CSS specificity order: inline style > ID selector > class/attribute/pseudo-class > element selector; later rules win ties.

HTTP is stateless; cookies, sessions, and tokens carry state between requests.

Responsive design uses fluid grids, flexible images, and media queries rather than fixed pixel layouts.

Accessibility essentials: alt text for images, label-input association, sufficient colour contrast, keyboard operability, and semantic heading order.

CIA triad: Confidentiality (authorised read only), Integrity (unauthorised modification prevented), Availability (timely access assured).

Symmetric encryption uses one shared key (AES, DES) and is fast; asymmetric uses a public/private pair (RSA) and solves key distribution but is slower.

Hashing is one-way and collision-resistant (SHA-256) and verifies integrity; it is not encryption because it cannot be reversed.

Digital signature = hash of message encrypted with sender's private key; verifies authenticity, integrity, and non-repudiation.

Malware classes: virus attaches to a host file, worm self-replicates across networks, trojan disguises as legitimate, ransomware encrypts and demands payment.

Phishing, pharming, and social engineering target the user rather than the technical perimeter; spam filters and user training reduce but do not eliminate risk.

Firewall types: packet-filtering inspects headers; stateful tracks connections; application-level proxies inspect payload.

Risk = likelihood x impact; controls are preventive, detective, or corrective, and residual risk remains after treatment.

Computer ethics codes (e.g. ACM/IEEE) cover honesty, competence, privacy, avoiding harm, and disclosure of conflicts; plagiarism and unauthorised access are violations.

Cloud service models: IaaS supplies virtual machines and storage, PaaS supplies a runtime and development platform, SaaS supplies finished applications.

Cloud deployment models: public, private, community, hybrid; measured by elasticity, on-demand self-service, and pay-per-use.

Machine learning types: supervised (labelled data), unsupervised (pattern discovery), reinforcement (reward signal); deep learning uses multi-layer neural networks.

IoT architecture layers: perception (sensors/actuators), network (connectivity), and application (services and analytics); constrained devices demand lightweight protocols such as MQTT.

Blockchain is an append-only distributed ledger of hash-linked blocks; consensus mechanisms include proof of work and proof of stake.

Big data characteristics (the Vs): volume, velocity, variety, veracity, and value; distributed processing frameworks handle data too large for one machine.

5G targets enhanced mobile broadband, ultra-reliable low-latency communication, and massive machine-type communication.

Quantum computing uses qubits with superposition and entanglement; Shor's algorithm threatens RSA and ECC, motivating post-quantum cryptography.

Augmented reality overlays digital content on the real world; virtual reality replaces it entirely; both raise issues of latency, comfort, and data privacy.