Tamil Nadu HSE First Year Computer Science key terms

A systematic way of writing numbers using a fixed set of digits and a base that determines each digit's place value. Binary, octal, decimal and hexadecimal are the systems most used in computing.

A base-2 number system that uses only the digits 0 and 1. Each position represents a power of two, and computers use it because electronic circuits have two stable states.

A base-8 number system using digits 0 to 7. It is used as a compact shorthand for binary, since each octal digit maps exactly to three binary digits.

A base-16 number system using digits 0 to 9 and letters A to F. One hexadecimal digit represents exactly four binary digits, so it is widely used to write memory addresses and colour codes compactly.

The smallest unit of digital information, holding a single value of either 0 or 1. Bits combine to form bytes, and they are the basic building block of all binary data representation.

A group of eight bits treated as one unit. It can store one character code, and multiples of bytes such as kilobytes and megabytes measure memory and storage capacity.

American Standard Code for Information Interchange, a character encoding that assigns a 7-bit numeric code to letters, digits, punctuation and control characters. It allows text to be stored and exchanged between systems.

A universal character encoding standard that assigns a unique code point to characters of almost every writing system. It overcomes the limited character range of ASCII and supports multilingual text.

A table that lists every possible combination of input values for a logic expression and shows the resulting output for each combination. It is used to verify and simplify Boolean expressions.

A branch of algebra in which variables take only the values 0 and 1, and operations follow logical rules. It provides the mathematical basis for designing digital circuits.

A physical electronic circuit that performs a basic Boolean operation on one or more binary inputs to produce a single output. AND, OR, NOT, NAND, NOR and XOR are common types.

A logic gate whose output is the inverse of the AND operation; it gives 0 only when all inputs are 1. It is called a universal gate because any other gate can be built from it.

A logic gate whose output is the inverse of the OR operation; it gives 1 only when all inputs are 0. Like NAND, it is a universal gate from which other gates can be constructed.

Two rules of Boolean algebra stating that the complement of a product equals the sum of the complements, and the complement of a sum equals the product of the complements. They help simplify circuits.

A named storage location in a program whose value can change during execution. In Python a variable is created by assignment and does not need an explicit type declaration.

A classification that determines what kind of values a variable can hold and which operations are allowed on them. Python's common types include int, float, str, bool and list.

Changing a value from one data type to another, either implicitly by the interpreter or explicitly by the programmer using functions such as int(), float() and str().

The rule that decides which operator is evaluated first in an expression containing several operators. In Python, exponentiation is evaluated before multiplication, which is evaluated before addition.

A combination of values, variables and operators that Python evaluates to produce a single result. An expression can be used wherever a value is expected.

A statement that stores a value in a variable using the equals sign. In Python the right-hand side is evaluated first, then bound to the name on the left.

The leading spaces at the start of a code line. Python uses indentation instead of braces to define blocks of statements, so inconsistent indentation raises an error.

A programming construct that determines the order in which statements execute. Selection structures choose between paths, and iteration structures repeat statements.

A control structure that repeats a block of statements while a condition holds or for each item in a sequence. Python provides for and while loops, with break and continue for control.

The repeated execution of a block of statements, once for each item of a sequence or while a condition remains true. It is the mechanism that loops rely on.

A named block of reusable code that performs a task and may accept arguments and return a value. It is defined with the def keyword and called by its name.

A value supplied to a function when it is called, which the function receives through its parameters. Arguments let one function work with different data on different calls.

The result that a function sends back to the code that called it, using the return statement. A function without a return statement gives back the value None.

An ordered sequence of characters enclosed in single, double or triple quotes. Strings are immutable in Python, so operations create new strings instead of changing existing ones.

The numeric position of an element in a sequence such as a string or list. Python indexing starts at 0, and negative indices count backwards from the end.

Extracting a part of a sequence by specifying start, stop and step values in square brackets. The stop index is excluded, and omitted values default to the sequence boundaries.

An ordered, mutable collection of items written in square brackets. Elements can be added, removed or replaced, and a list may hold items of different types.

An ordered, immutable collection of items written in parentheses. Once created it cannot be changed, so it is used for fixed groups of related values.

A mutable collection of key-value pairs written in curly braces. Keys must be unique and immutable, and values are accessed by key rather than by numeric position.

The Central Processing Unit, which fetches, decodes and executes program instructions. It contains the arithmetic logic unit, the control unit and registers, and is often called the brain of the computer.

The Arithmetic Logic Unit inside the CPU that performs arithmetic operations such as addition and logical operations such as comparison and AND. It works on data held in registers.

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

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

Random Access Memory, the main volatile memory where programs and data are held while the computer runs. Its contents are lost when power is switched off.

Read Only Memory, a non-volatile memory whose contents are written during manufacture and normally cannot be changed. It stores firmware such as the start-up instructions used at boot time.

System software that manages hardware resources, provides services to application programs and offers a user interface. Examples include Windows, Linux and Android.

A program in execution, together with its current state, memory and resources. The operating system creates, schedules and terminates processes.

A set of agreed rules that governs how data is formatted, transmitted and received across a network. TCP, IP and HTTP are widely used protocols.

A unique numeric label assigned to a device on a network so that data can be routed to it. IPv4 uses 32 bits, while IPv6 uses 128 bits.

The maximum amount of data that a communication channel can carry in a given time, usually measured in bits per second. Higher bandwidth allows faster transfer of information.

Any illegal activity carried out using computers or networks, such as hacking, identity theft, phishing or spreading malware. It is punishable under information technology laws.

A fraudulent attempt to obtain sensitive information such as passwords or card numbers by pretending to be a trustworthy entity in email, messages or fake websites.

Software written with malicious intent, including viruses, worms, trojans and ransomware. It can damage systems, steal data or give attackers unauthorised access.

A hardware or software filter that monitors incoming and outgoing network traffic and blocks connections that violate security rules. It helps protect a system from unauthorised access.

The practice of protecting computers, networks and data from digital attacks through measures such as strong passwords, encryption, updates and safe online behaviour.

The delivery of computing services such as storage, processing and software over the internet on demand. Users pay for what they use instead of owning physical infrastructure.

The field of computing concerned with building systems that perform tasks normally requiring human intelligence, such as learning, reasoning and language understanding.

A network of everyday physical devices embedded with sensors and software that collect and exchange data over the internet without direct human intervention.