BSEB Inter Computer Science key terms

An electronic machine that accepts data, carries out arithmetic and logical operations on it under the control of stored instructions, and produces useful information as output.

Raw, unprocessed facts, numbers, words or symbols collected from a source. On its own data has little meaning until it is organised and interpreted by a computer.

Hardware that sends data or commands from the outside world into a computer, such as a keyboard, mouse, scanner or microphone. The computer converts the signal into a form it can process.

A group of eight binary digits treated as one unit. A byte can store one character such as a letter or digit, and larger amounts of memory are measured in kilobytes, megabytes and gigabytes.

A positional number system that uses only two digits, 0 and 1, with each place value being a power of two. It is the natural language of digital circuits, where 0 and 1 represent low and high voltage.

A base-16 number system using digits 0 to 9 and letters A to F. Because one hexadecimal digit matches exactly four binary bits, it gives programmers a short, readable way to write long binary values.

A method of representing signed integers in binary in which the leftmost bit gives the sign. A negative number is formed by inverting all bits of its positive form and adding one, which makes subtraction simple for the processor.

A branch of algebra in which variables take only the values true or false, written 1 and 0, and are combined with AND, OR and NOT. It provides the rules used to design and simplify digital logic circuits.

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

The central processing unit is the part of a computer that fetches instructions from memory, decodes them and carries them out. It contains the arithmetic logic unit, the control unit and registers.

The arithmetic logic unit is the section of the processor that performs calculations such as addition and subtraction and logical comparisons such as AND, OR and greater-than. Its result is stored in a register.

Random access memory is the main working memory of a computer. It holds programs and data currently in use, allows any location to be read or written quickly, and loses its contents when power is switched off.

Read only memory is non-volatile memory whose contents are written at manufacture and normally cannot be changed by the user. It stores the start-up instructions a computer needs when it is powered on.

Programs that manage the computer itself and provide a platform for other programs, including operating systems, device drivers, translators and utility programs. Users normally do not run it to do a specific job like writing a letter.

A translator that reads a complete source program written in a high-level language and converts it into machine code in one go. Errors are reported after the whole program is examined, and an object file is produced.

The master program that starts when a computer is switched on and controls all other software. It manages memory, processor time, files and devices, and provides the interface through which users run programs.

A graphical user interface lets a person operate a computer by clicking pictures, icons, menus and buttons instead of typing commands. Windows, icons, menus and a pointer are its main elements.

The process of starting a computer by loading the operating system from secondary storage into memory. A cold boot starts a switched-off machine, while a warm boot restarts one that is already running.

A named collection of related data stored on a disk, such as a document, picture or program. The operating system records its name, size, location and dates, and lets programs open, read and save it.

A named memory location in a program whose stored value can change while the program runs. In C every variable must be declared with a data type before it is used.

A classification that tells the compiler what kind of values a variable may hold and how much memory it needs. C provides int, float, double, char and void, plus derived types such as arrays and structures.

A statement that changes the order in which a program's instructions run. C offers sequence, selection with if and switch, and repetition with for, while and do-while loops.

A block of code with a name that performs a task and can be called from other parts of a program. Functions may take arguments, may return a value, and help avoid repeating the same code.

A collection of elements of the same data type stored in consecutive memory locations and accessed by an index. In C the index starts at zero, and the size must be fixed when the array is declared.

A variable that stores the memory address of another variable rather than a value. Pointers allow a program to refer to data indirectly, to pass large structures efficiently and to build linked lists and trees.

A linear data structure in which insertion and deletion both happen at one end called the top. It follows the last in, first out rule, so the item added most recently is removed first.

A linear data structure in which items are added at one end, the rear, and removed from the other end, the front. It follows the first in, first out rule, like a line of people waiting for service.

A collection of nodes that need not be stored next to each other in memory, where each node holds data plus a pointer to the next node. It can grow or shrink easily but does not allow direct access by index.

Database management system: software that stores, organises and controls access to a database. It lets many users share data safely, enforces rules and constraints, and answers queries written in a language such as SQL.

A column or set of columns whose value uniquely identifies each row of a table. It cannot be null and cannot repeat, and other tables may refer to it through a foreign key.

A column in one table that holds the value of the primary key of another table, creating a link between the two. It keeps data consistent by allowing only values that exist in the referenced table.

Structured query language, the standard language for working with relational databases. It provides statements to create tables, insert, update and delete rows, and retrieve data with SELECT queries.

A numeric label given to every device on an internet protocol network so that data can be routed to it. IPv4 uses four numbers from 0 to 255 separated by dots.

A set of agreed rules that governs how computers exchange data over a network. Protocols define message formats, timing and the actions to take on errors; TCP/IP is the basis of the internet.

A device that connects separate networks and forwards data packets towards their destination by choosing the best path from its routing table. Home routers also link a local network to an internet service provider.

Hypertext markup language, the language used to write web pages. It marks up content with tags such as headings, paragraphs, lists and links, and browsers read it to display the page.

A program that requests web pages from servers, interprets the HTML and displays the result on screen. Examples include Chrome, Firefox and Edge; browsers also run scripts and store cookies.

A cyber attack in which a criminal sends fake emails, messages or websites that pretend to come from a trusted organisation, in order to trick people into revealing passwords, card numbers or other private details.