MATSEC IM Information Technology cheat sheet

Data vs information: data is raw unprocessed symbols (numbers, characters, signals); information is data that has been processed, organised and given context so it is meaningful to a recipient. Knowledge applies information to decisions.

Characteristics used to judge information quality: accuracy, relevance, timeliness, completeness, accessibility, cost-effectiveness and verifiability. A single wrong field makes a record inaccurate even if all other fields are correct.

The information processing cycle: input → processing → output, with storage as an accompanying activity and feedback/control as a refinement. Input devices capture data; output devices present results; storage retains data between stages.

Hardware categories: input, output, storage, processing (CPU) and communication devices. A touchscreen is both input and output; a barcode reader is input only; a plotter is output only.

CPU components: control unit fetches and decodes instructions and coordinates the datapath; ALU performs arithmetic and logic operations; registers (PC, IR, MAR, MDR, accumulator) hold the current instruction and operands.

Von Neumann architecture stores program instructions and data in the same memory; the fetch–decode–execute cycle repeats continuously. Clock speed is measured in hertz; a 3 GHz clock allows up to 3 billion cycles per second.

Memory hierarchy from fastest/smallest/most expensive to slowest/largest/cheapest: registers → cache → main memory (RAM) → secondary storage → tertiary/offline storage. Cache exploits locality of reference.

RAM is volatile and directly addressable by the CPU; ROM is non-volatile and typically holds firmware such as the bootstrap loader. Flash memory is non-volatile and rewritable, used in SSDs and USB drives.

Storage capacity units: 1 byte = 8 bits; 1 KB = 1024 bytes; 1 MB = 1024 KB; 1 GB = 1024 MB; 1 TB = 1024 GB. Access time (latency) and transfer rate distinguish storage devices more than raw capacity.

System software (operating systems, utilities, device drivers, language translators) manages hardware and provides a platform; application software (word processors, spreadsheets, DBMS, browsers) performs user tasks.

Operating system functions: process management and scheduling, memory management (allocation, paging, virtual memory), file management, device management via drivers, security/access control and a user interface.

Utility programs include antivirus, disk defragmenter, backup, compression and disk-cleanup tools. A defragmenter reorganises file fragments to improve sequential read performance on magnetic disks.

Translators: a compiler translates the whole source program into object code before execution; an interpreter translates and executes statement by statement; an assembler translates assembly language into machine code.

Programming constructs: sequence, selection (IF/CASE) and iteration (FOR, WHILE, REPEAT). A FOR loop runs a known number of times; a WHILE loop tests the condition before the body; a REPEAT loop tests after.

Data types: integer, real/float, character, string, Boolean and date. Validation checks type, range, presence, length and format; verification checks accuracy by double entry or visual comparison.

Database terminology: table/relation, record/tuple, field/attribute, primary key (unique identifier), foreign key (links to another table's primary key), candidate key and composite key.

Normalisation: 1NF removes repeating groups so each field holds atomic values; 2NF removes partial dependencies on part of a composite key; 3NF removes transitive dependencies on non-key fields.

SQL fundamentals: SELECT columns FROM table WHERE condition; ORDER BY sorts; GROUP BY aggregates with COUNT, SUM, AVG, MIN, MAX; INSERT INTO adds rows; UPDATE modifies rows; DELETE removes rows.

File organisation: serial (records in arrival order), sequential (ordered by key, efficient for batch), direct/random access (hash or index, fast single-record retrieval), and indexed sequential (hybrid).

Network topologies: star (central switch, single point of failure), bus (shared backbone, collisions), ring (token passing), mesh (redundant paths, high cabling cost). Physical vs logical topology may differ.

LAN covers a limited area such as one building; WAN spans large distances and often uses leased lines; MAN covers a city. The Internet is a network of networks using TCP/IP.

IP address identifies a host; a subnet mask separates network and host portions; a default gateway routes traffic off the local subnet; DNS resolves domain names to IP addresses; DHCP assigns IP addresses automatically.

Transmission media: twisted pair (cheap, susceptible to interference), coaxial, fibre optic (high bandwidth, immune to electromagnetic interference), and wireless (radio, microwave, infrared).

Bandwidth is the range/capacity of a channel; latency is delay; throughput is actual data transferred per unit time. Serial transmission sends bits one at a time; parallel sends several simultaneously over separate lines.

Malware types: virus (attaches to a host file), worm (self-replicating across networks), Trojan (disguised as legitimate software), spyware (collects data covertly), ransomware (encrypts data for payment), rootkit (hides privileged access).

Threats and defences: phishing and pharming target credentials; DoS floods a service; brute force tries many passwords. Defences include firewalls, encryption, authentication (something you know/have/are), access rights and patching.

Symmetric encryption uses one shared key (fast, key-distribution problem); asymmetric uses a public/private key pair (slower, solves key exchange); hashing is one-way and used for integrity and password storage.

Legal and ethical issues: data protection legislation governs personal data processing (lawful basis, purpose limitation, data subject rights); computer misuse law covers unauthorised access; copyright covers software and digital content.

Health and safety and environmental issues: RSI and eyestrain from prolonged use, ergonomic seating and screen positioning, e-waste recycling, energy consumption of data centres, and digital divide concerns.