NSSCAS Computer Science (8231) key terms

A method of representing signed integers in binary where the most significant bit indicates the sign; negative values are formed by inverting all bits of the positive value and adding one.

A base-16 number system using digits 0–9 and letters A–F. It is widely used in computing as a compact, human-readable shorthand for binary values, especially memory addresses and colour codes.

A way of storing real numbers as a sign, a mantissa and an exponent. Moving the binary point lets the same number of bits represent very large and very small values, but precision is limited.

A defined list of characters and the unique binary codes used to represent them. ASCII covers basic English characters, while Unicode supports many languages and symbols from around the world.

A set of agreed rules and conventions that governs how devices exchange data over a network. Protocols define message formats, timing, error handling and addressing, allowing hardware and software from different makers to communicate.

A network transmission method in which data is split into small packets that travel independently and are reassembled at the destination. It makes efficient use of shared links and can route around failures.

A numeric label assigned to a device or interface on a network so data can be routed to it. IPv4 uses 32-bit addresses, while IPv6 uses 128-bit addresses to provide many more unique values.

A distributed naming service that translates human-readable domain names into IP addresses. DNS servers store records and resolve queries so users do not need to remember numeric addresses.

A computer design in which program instructions and data are stored together in the same memory. The processor fetches instructions and data from memory over a shared bus, one instruction at a time.

The repeated process in which a processor fetches an instruction from memory, decodes it to determine the operation, and executes it. The program counter tracks the next instruction address.

A small, fast memory between the processor and main memory that stores frequently used instructions and data. It reduces average access time because the processor waits less often for slower RAM.

System software that manages hardware, runs application programs and provides common services such as memory allocation, file management, scheduling and user interfaces.

A translator that converts a whole program written in a high-level language into machine code before it is run. It reports errors after analysing the complete source code and produces an executable file.

A technique that uses part of secondary storage as an extension of RAM. Pages of memory are swapped between disk and RAM so programs larger than physical memory can run, though performance may suffer.

The process of converting readable data into an unreadable form using a key, so that only authorised parties can recover the original. It protects confidentiality during storage and transmission.

A one-way function that turns data into a fixed-length value called a hash. The same input always gives the same hash, but the original cannot practically be recovered, making hashes useful for integrity checks and password storage.

An encrypted hash or equivalent cryptographic value attached to a message to prove its origin and integrity. It helps the receiver confirm who sent the data and that it has not been altered.

Hardware or software that filters network traffic against a set of rules, blocking unauthorised connections while allowing permitted ones. It forms a barrier between a private network and external networks such as the internet.

Automated checks that test whether input data is reasonable and follows expected rules, such as range checks, type checks and presence checks. Validation cannot prove data is correct, only that it is plausible.

Checks that aim to confirm data has been copied or entered accurately, for example double entry, visual checking or parity checks. Verification compares data with its source rather than testing whether the value is logically acceptable.

A legal right that gives the creator of an original work control over how it is copied, distributed and adapted. Software, music, images and text are protected, usually for a fixed period.

A software licence that makes source code available and allows users to study, modify and redistribute it under stated conditions. Examples include the GNU General Public License and MIT licence.

Laws that regulate how personal data is collected, stored, used and shared. They typically require organisations to process data fairly, keep it secure and allow individuals to access or correct it.

A field or combination of fields that uniquely identifies each record in a table. It cannot contain duplicate values or nulls, and it is used to establish relationships with other tables.

A field in one table that refers to the primary key of another table, creating a link between the two. It enforces referential integrity by ensuring that related records exist.

The process of organising database tables to reduce redundant data and avoid update anomalies. It usually involves applying rules called normal forms, moving repeated groups into separate related tables.

Structured Query Language. A standard language for creating, querying and updating relational databases. Commands such as SELECT, INSERT, UPDATE and DELETE let users manipulate data and define database structures.

A finite sequence of unambiguous steps that solves a problem or performs a task. It must produce a result in a reasonable time and can be represented in pseudocode, flowcharts or a programming language.

A structured, informal notation for expressing algorithms using programming-like statements without the strict syntax of a real language. It helps designers communicate logic before coding.

Breaking a complex problem into smaller, manageable sub-problems that can be solved separately and then combined. It makes algorithms easier to design, test and maintain.

An efficient search algorithm that repeatedly halves a sorted list, comparing the target with the middle item. It is much faster than linear search for large lists but requires the data to be ordered.

A data structure that stores a fixed number of items of the same type in contiguous memory, accessed by an index. It allows fast direct access but usually cannot grow or shrink at run time.

A dynamic data structure made of nodes, where each node stores data and a pointer to the next node. Items do not need contiguous memory, so insertion and deletion are easy, but access is sequential.

A last-in, first-out data structure in which items are added and removed at one end called the top. It is used for function calls, undo operations and expression evaluation.

A first-in, first-out data structure in which items are added at the rear and removed from the front. It is used for scheduling tasks, buffering data and managing waiting lines.

A programming technique in which a function calls itself to solve a smaller version of the same problem. Every recursive solution needs a base case to stop the calls and prevent infinite recursion.

A structured process for planning, creating, testing and maintaining software. Common stages include requirements analysis, design, implementation, testing, deployment and maintenance.

A software development approach based on short iterative cycles, continuous customer feedback and flexible response to change. Work is delivered in small increments rather than one large release at the end.

A sequential software development model in which each stage is completed before the next begins. It is easy to manage but inflexible, because returning to an earlier stage is costly.

Testing individual components or functions in isolation to verify that each behaves as specified. It is usually automated and performed by developers before components are integrated.