Tamil Nadu HSE Second Year Computer Applications key terms

The smallest unit of data in a computer, holding a single binary value of either 0 or 1. Groups of bits represent numbers, characters, and instructions.

A group of eight bits treated as one unit. It commonly stores one character, and memory and storage sizes are measured in multiples of bytes.

A base-2 number system that uses only the digits 0 and 1, with each position representing a power of two. Computers use it because circuits have two stable states.

A base-8 number system using digits 0 to 7. Each octal digit corresponds to exactly three binary bits, so it is a compact shorthand for binary values.

A base-16 number system using digits 0 to 9 and letters A to F. Each hex digit maps to four binary bits, making it a compact way to write memory addresses and colour codes.

American Standard Code for Information Interchange, a character encoding that assigns numeric codes to letters, digits, punctuation, and control characters. Standard ASCII uses seven bits for 128 codes.

A universal character encoding standard that assigns a unique code point to characters of most of the world's writing systems, including Tamil, so text can be exchanged across platforms.

The main processor of a computer that fetches, decodes, and executes instructions. It contains the arithmetic logic unit, control unit, and registers, and is often called the brain of the computer.

The part of the CPU that performs arithmetic operations such as addition and subtraction and logical operations such as AND, OR, and comparison of values.

The CPU component that directs the operation of the computer by decoding instructions and generating control signals that coordinate memory, input, output, and the arithmetic logic unit.

A small, very fast storage location inside the CPU used to hold data, addresses, or intermediate results during instruction execution. Registers are far faster than main memory.

A small, high-speed memory placed between the CPU and main memory that stores frequently used instructions and data to reduce average access time.

Volatile main memory that holds programs and data currently in use. Its contents are lost when power is switched off, and any location can be accessed directly.

Non-volatile memory whose contents are retained when power is off and which normally cannot be rewritten by ordinary programs. It stores firmware such as the boot instructions.

The process of starting a computer, in which firmware runs power-on self-tests and then loads the operating system from secondary storage into main memory.

System software that manages hardware resources, provides file and process management, and offers services that application programs use. Examples include Windows, Linux, and Android.

A translator program that converts an entire source program written in a high-level language into machine code before execution, reporting errors for the whole program at once.

A translator that reads a source program line by line, converting and executing each statement in turn. It is easier to debug but generally slower than a compiler.

A finite, ordered set of unambiguous steps that solves a problem or performs a task, with clearly defined input and output and guaranteed termination.

A diagram that represents an algorithm using standard symbols such as ovals for start and end, parallelograms for input and output, rectangles for processes, and diamonds for decisions.

A structured, English-like description of an algorithm that uses programming constructs without strict syntax rules, helping programmers plan logic before coding.

A named memory location whose stored value can change during program execution. In C++ and Python a variable must be created with a name and given a value before use.

A classification that specifies which kind of values a variable can hold, such as integer, floating point, character, or string, and which operations are valid on those values.

Changing a value from one data type to another, either implicitly by the compiler or explicitly by the programmer. Converting a float to an int discards the fractional part.

A control structure that executes a block of statements only when a specified condition is true, with optional alternative blocks. C++ uses if and switch; Python uses if, elif, and else.

A control structure that repeats a set of statements while a condition holds or for a fixed number of iterations. Common forms are while, do-while, and for loops.

A loop placed inside the body of another loop. The inner loop completes all its iterations for each single iteration of the outer loop, which is useful for tables and patterns.

A named block of statements that performs a specific task and can be called repeatedly, optionally receiving arguments and returning a value. Functions promote reuse and modularity.

A variable declared in a function definition that receives a value when the function is called. The matching value supplied by the caller is called an argument.

A collection of elements of the same data type stored in consecutive memory locations and accessed by an index, which in C++ starts at zero.

A sequence of characters treated as a single value, such as a name or sentence. In C++ it may be a character array or the string class; Python has a built-in str type.

A column or set of columns whose value uniquely identifies each row of a table. It must be unique and cannot contain null values.

A column in one table whose values must match a primary key value in another table, creating a link between the tables and enforcing referential integrity.

A database rule ensuring that a foreign key value always refers to an existing primary key value, or is null, so that relationships between tables stay consistent.

A standard language for defining, manipulating, and querying relational databases. Statements such as SELECT, INSERT, UPDATE, DELETE, and CREATE TABLE are grouped into DDL and DML.

A numeric address that uniquely identifies a device on a network so data can be routed to it. IPv4 addresses are 32-bit; IPv6 addresses are 128-bit.

A hierarchical naming service that translates human-readable domain names such as example.com into the numeric IP addresses that computers use to locate servers.

A set of agreed rules governing how data is formatted, transmitted, and acknowledged between devices on a network. Examples include TCP, IP, HTTP, and FTP.

HyperText Transfer Protocol, the request-response protocol used by web browsers and servers to transfer web pages and other resources. HTTPS adds encryption for security.

The address of a resource on the web, consisting of a scheme such as https, a host name, an optional path, and optional query parameters.

HyperText Markup Language, the standard language for describing the structure and content of web pages using elements marked by tags such as headings, paragraphs, lists, and links.

A markup instruction in HTML enclosed in angle brackets that defines an element. Most elements have an opening tag and a closing tag, and may carry attributes.

A name-value pair written inside an HTML opening tag that supplies extra information about the element, such as src for an image or href for a hyperlink.

Cascading Style Sheets, a language used to control the presentation of HTML documents, including colours, fonts, spacing, and layout, kept separate from content.

The part of a CSS rule that identifies which HTML elements the declarations apply to, for example an element name, a class, or an id.

Delivery of computing services such as storage, processing, and software over the internet on demand, usually charged by usage and offered as IaaS, PaaS, or SaaS.

A network of physical devices embedded with sensors and software that collect and exchange data over the internet, enabling remote monitoring and automation.

The branch of computing concerned with building systems that perform tasks associated with human intelligence, such as learning, reasoning, language understanding, and pattern recognition.

A subfield of artificial intelligence in which programs improve their performance on a task by learning patterns from data rather than following only explicitly written rules.

Buying and selling of goods and services over electronic networks such as the internet. Common models include business-to-business, business-to-consumer, and consumer-to-consumer.

A cyber attack in which a fraudster impersonates a trusted organisation through fake emails, messages, or websites to trick a user into revealing passwords, OTPs, or bank details.

Malicious software designed to damage, disrupt, or gain unauthorised access to a computer system. It includes viruses, worms, trojans, spyware, and ransomware.

Hardware or software that monitors and filters incoming and outgoing network traffic according to security rules, blocking unauthorised access while permitting legitimate communication.