CAPE Information Technology Unit 1 cheat sheet

Data is raw, unprocessed facts (numbers, text, images); information is data that has been processed, organised and given context so it has meaning and value to a user.

Characteristics of good information: accuracy, relevance, timeliness, completeness, verifiability, cost-effectiveness, flexibility and simplicity.

Data processing cycle: input → validation → processing → storage → output; feedback from output can trigger new input.

Hardware categories: input devices, output devices, processing units (CPU), storage (primary: RAM/ROM; secondary: HDD/SSD/optical), and communication devices.

CPU fetch-decode-execute cycle: fetch instruction from memory using the program counter, decode it in the control unit, execute in the ALU, store result in registers.

Memory hierarchy from fastest/costliest to slowest/cheapest: CPU registers → cache → RAM → secondary storage → offline/archival storage.

System software (operating systems, utilities, translators) manages hardware; application software (general-purpose, special-purpose, custom-written) performs user tasks.

Types of computers by scale: supercomputer, mainframe, minicomputer/midrange, microcomputer (desktop, laptop, tablet, smartphone), embedded systems.

A system is a set of interrelated components with input, processing, output and feedback operating within an environment; subsystems interact to achieve a common goal.

RAM is volatile and read/write; ROM is non-volatile and read-only. RAM stores the OS, running programs and data currently in use.

Cache memory sits between CPU and RAM; L1 is fastest and smallest, L3 is largest and slowest of the cache levels.

Storage capacity order: bit < nibble (4 bits) < byte (8 bits) < kilobyte < megabyte < gigabyte < terabyte < petabyte.

Input devices: keyboard, mouse, scanner, microphone, barcode reader, OMR, OCR, MICR, biometric sensors, touch screen, light pen, joystick, webcam.

Output devices: monitor (CRT, LCD, LED, OLED), printer (impact: dot matrix, daisy wheel; non-impact: inkjet, laser, thermal), plotter, speaker, projector.

Software types: system software (OS, utility programs, language translators, device drivers) versus application software (word processors, spreadsheets, DBMS, browsers).

Operating system functions: process management, memory management, file management, device management, security, user interface, and providing a platform for applications.

Utility programs: antivirus, backup, disk defragmenter, disk cleanup, compression, file manager, screen saver, firewall.

Programming language translators: compiler (whole program at once), interpreter (line by line), assembler (assembly to machine code).

Data hierarchy: bit → byte/character → field → record → file → database.

Database approach advantages: reduced redundancy, improved consistency, shared data, better security, data independence, backup/recovery, concurrent access.

DBMS components: data definition language (DDL), data manipulation language (DML), data control language (DCL), data dictionary, query facility, report generator.

Relational model terms: relation (table), tuple (row/record), attribute (column/field), primary key (unique identifier), foreign key (links to another table's primary key), candidate key, composite key.

Entity-relationship model: entity, attribute, relationship, cardinality (1:1, 1:M, M:N); ER diagrams use rectangles for entities, diamonds for relationships, ovals for attributes.

Normalisation removes redundancy and anomalies: 1NF (atomic values), 2NF (1NF + no partial dependency), 3NF (2NF + no transitive dependency).

Data validation checks: range, type, format, presence, length, consistency, check digit; verification confirms data was copied/entered correctly (double entry, visual check).

File organisation methods: sequential (records in order, good for batch), direct/random (access by key, good for real-time), indexed sequential (index plus sequential data).

Data warehousing collects integrated, subject-oriented, time-variant, non-volatile data for analysis; data mining finds patterns; OLAP supports multidimensional analysis.