CAPE Information Technology Unit 1 flashcards

33 cards. Read the term and the definition here. The deck at the top of this page is optional.

Data versus information

Data is raw, unprocessed facts and figures with no meaning on its own. Information is data that has been processed, organised and given context so it becomes meaningful and useful for decision-making.

Data processing cycle

The sequence of stages data passes through: input, validation, processing, storage and output. Feedback from output can be used to adjust future input and processing.

Characteristics of good information

Accurate, relevant, timely, complete, verifiable, cost-effective, flexible and simple. Information lacking these qualities is unreliable for decision-making and may mislead users.

Fetch-decode-execute cycle

The CPU repeatedly fetches an instruction from memory, decodes it in the control unit, executes it in the ALU, and stores the result. The program counter tracks the next instruction.

System software

Software that manages hardware and provides a platform for applications. Examples include operating systems, utility programs, device drivers and language translators such as compilers and interpreters.

Application software

Software designed to perform user tasks. General-purpose packages (word processors, spreadsheets), special-purpose packages (payroll, stock control) and custom-written software are the main categories.

Input devices

Devices that feed data into a computer. Examples include keyboards, mice, scanners, microphones, barcode readers, OMR, OCR, MICR, biometric sensors, touch screens and webcams.

Output devices

Devices that present processed data to the user. Examples include monitors, printers (impact and non-impact), plotters, speakers and projectors.

Memory hierarchy

Order of storage from fastest and costliest to slowest and cheapest: CPU registers, cache, RAM, secondary storage, offline storage. Faster levels are smaller and closer to the CPU.

Types of computers by scale

Supercomputers (fastest, scientific), mainframes (bulk processing), minicomputers, microcomputers (desktops, laptops, tablets, phones) and embedded systems (dedicated within devices).

System concept

A system is a set of interrelated components with input, processing, output and feedback operating in an environment. Subsystems interact to achieve a shared goal.

RAM versus ROM

RAM is volatile, read/write, and holds the operating system, running programs and active data. ROM is non-volatile, read-only, and stores firmware such as the boot program.

Cache memory

Fast memory between the CPU and RAM that stores frequently used instructions and data. L1 is fastest and smallest; L3 is largest and slowest.

Storage capacity units

Bit < nibble (4 bits) < byte (8 bits) < kilobyte < megabyte < gigabyte < terabyte < petabyte. A byte typically represents one character.

Operating system functions

Process management, memory management, file management, device management, security and user interface. The OS also provides a platform on which applications run.

Utility programs

Programs that maintain and optimise the system: antivirus, backup, disk defragmenter, disk cleanup, compression tools, file managers, screen savers and firewalls.

Compiler versus interpreter

A compiler translates the whole program into machine code before execution. An interpreter translates and executes one line at a time, which is slower but easier to debug.

Assembler

A translator that converts assembly language (mnemonic instructions) into machine code. It is used for low-level programming and produces efficient, hardware-specific code.

Impact versus non-impact printers

Impact printers (dot matrix, daisy wheel) strike a ribbon against paper. Non-impact printers (inkjet, laser, thermal) do not strike and are quieter and generally faster.

Monitor technologies

CRT (older, bulky), LCD (liquid crystal), LED (backlit LCD) and OLED (self-emitting pixels). OLED offers deeper blacks and thinner panels than LCD.

Primary versus secondary storage

Primary storage (RAM, ROM, cache) is fast and directly accessed by the CPU. Secondary storage (HDD, SSD, optical, USB) is slower, larger, non-volatile and used for permanent data.

Data hierarchy

Order of data organisation: bit, byte/character, field, record, file, database. Each level groups and structures the level below it.

Database approach advantages

Reduced data redundancy, improved consistency, shared data, better security, data independence, backup and recovery, and controlled concurrent access by multiple users.

DBMS components

Data definition language (DDL), data manipulation language (DML), data control language (DCL), data dictionary, query facility and report generator. The DBMS manages storage and access.

Primary key

A field or combination of fields that uniquely identifies each record in a table. Primary keys cannot contain duplicate values or nulls.

Foreign key

A field in one table that refers to the primary key of another table. Foreign keys enforce referential integrity and link related tables.

Entity-relationship model

A conceptual model of entities, attributes and relationships. ER diagrams use rectangles for entities, ovals for attributes and diamonds for relationships, with cardinality 1:1, 1:M or M:N.

Normalisation

A process of organising tables to remove redundancy and anomalies. 1NF requires atomic values, 2NF removes partial dependencies, 3NF removes transitive dependencies.

Data validation

Checks that data is reasonable before processing: range, type, format, presence, length, consistency and check-digit checks. Validation cannot confirm that data is correct.

Data verification

Confirms data was entered or copied correctly. Methods include double entry, visual checking, parity checks and hash totals.

File organisation methods

Sequential (records in order, good for batch), direct/random (access by key, good for real-time) and indexed sequential (index plus sequential data). Choice depends on access pattern.

Data warehouse

A large, central store of integrated, subject-oriented, time-variant and non-volatile data used for analysis and reporting rather than day-to-day transactions.

Data mining

The process of extracting useful patterns, trends and relationships from large data sets using statistical and machine-learning techniques to support decision-making.