CHSE Odisha Elective Computer Science key terms

The part of the CPU that performs arithmetic operations such as addition and subtraction and logical operations such as AND, OR and comparison. It works on values held in registers and returns results there.

A small, fast memory placed between the CPU and main memory that keeps recently or frequently used instructions and data. It reduces average access time because most requests are served without waiting for slower RAM.

A very small, very fast storage location inside the CPU used to hold an instruction, an address or an operand while it is being processed. Registers are far faster than cache or RAM.

A computer design in which program instructions and data share the same memory and travel over the same bus to the CPU. Executing an instruction normally needs fetch, decode and execute steps.

A set of shared wires or channels that carries data, addresses and control signals between the CPU, memory and input/output devices. Only one transfer can use the bus at a time.

A way of writing signed binary numbers in which the leftmost bit gives the sign and a negative value is formed by inverting all bits and adding one. Subtraction then becomes addition.

A base-16 number system using digits 0 to 9 and letters A to F. One hexadecimal digit represents exactly four binary bits, so it writes byte values and memory addresses compactly.

Binary Coded Decimal: a representation in which each decimal digit is stored separately in four bits. Decimal fractions stay exact, but it wastes storage compared with pure binary.

American Standard Code for Information Interchange: a character code that gives a 7-bit number to letters, digits, punctuation and control characters. Its 8-bit extension underlies most text files.

The condition where the result of an arithmetic operation needs more bits than the fixed word length can hold, so the stored value is wrong. Signed overflow is detected when the carry into the sign bit differs from the carry out of it.

A table listing every possible combination of input values for a Boolean expression or logic circuit together with the output produced for each combination. With n inputs it has 2 to the power n rows.

Two Boolean identities: the complement of A AND B equals (not A) OR (not B), and the complement of A OR B equals (not A) AND (not B). They allow circuits to be rewritten using one gate type.

A logic gate whose output is 0 only when all its inputs are 1; it is an AND gate followed by a NOT. NAND is called a universal gate because any other gate can be built from it.

A grid diagram that arranges the cells of a truth table so that neighbouring cells differ in only one variable. Grouping adjacent 1s gives a simplified Boolean expression without long algebra.

A combinational circuit that adds two single bits and produces a sum and a carry output. Sum equals A XOR B and carry equals A AND B; a full adder also accepts an incoming carry.

A combinational circuit with several data inputs, a set of select lines and one output. The select code decides which input reaches the output, so it works as a data selector.

A variable that stores the memory address of another variable or object. Dereferencing it with the * operator accesses the stored value; pointers enable dynamic memory and pass-by-reference.

A technique in which a function calls itself with a smaller version of the same problem and stops when a base case is reached. Each call uses a stack frame, so deep recursion can exhaust memory.

A parameter-passing method in which the function receives the address of the caller's argument, so changes made through the pointer are visible in the caller. In C it is simulated using pointers.

The byte with value zero, written as '\0', that marks the end of a C character string. Functions such as strlen and printf stop at it, so a string array must reserve room for it.

A value of type FILE * returned by fopen that identifies an open file and tracks the current read or write position. Functions such as fprintf, fgets and fclose take it as an argument.

A linear data structure in which insertion and deletion happen only at one end, the top, so the last item pushed is the first popped. It supports function calls, expression evaluation and backtracking.

A linear data structure in which items are inserted at the rear and deleted from the front, giving first-in-first-out order. A circular array or a linked list avoids wasting space.

A collection of nodes, each holding data and a pointer to the next node, so the elements need not sit in consecutive memory. Insertion and deletion are cheap, but access requires traversal.

A search on a sorted array that compares the target with the middle element and discards the half that cannot contain it. Each step halves the range, giving logarithmic running time.

A sorting method that repeatedly compares neighbouring elements and swaps them when they are out of order, so large values drift towards the end. It is easy to code but slow on large lists.

A column or minimal group of columns whose values uniquely identify each row of a table. It must be unique and never null, and each table should have exactly one.

A column or group of columns in one table that refers to the primary key of another table, enforcing referential integrity. It may repeat and may be null, but non-null values must match a parent row.

The process of organising tables so that redundancy and insertion, update and deletion anomalies are reduced, usually by splitting data into related tables. The common stages are 1NF, 2NF and 3NF.

An operation that combines rows from two or more tables using a matching condition, usually equality between a foreign key and a primary key. Inner joins keep matches only; outer joins also keep unmatched rows.

Data Definition Language: the SQL statements such as CREATE, ALTER and DROP that define, change or remove the structure of database objects. They alter the schema rather than the rows stored in tables.

Data Manipulation Language: SQL statements such as INSERT, UPDATE and DELETE, and usually SELECT, that work on the rows stored in tables rather than on the structure of those tables.

A numeric label given to a device on a network so that packets can be routed to it. IPv4 uses 32 bits written as four decimal numbers; IPv6 uses 128 bits written in hexadecimal.

Domain Name System: a worldwide distributed service that translates readable domain names into IP addresses. Resolvers ask a hierarchy of name servers and cache the answers they receive.

A device that joins different networks and forwards packets between them by looking up the destination IP address in a routing table. Home routers also perform NAT and often provide Wi-Fi.

Hypertext Transfer Protocol: the request-response protocol a browser uses to fetch web pages. A request names a method and a URL, and the response carries a status code such as 200 or 404.

Hypertext Markup Language: the markup language that describes the structure of a web page using elements such as headings, paragraphs, lists, links and images, which the browser then renders.

Uniform Resource Locator: the address of a resource on the web, giving the scheme, the server name and the path of the file, for example https://example.com/page.html.

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

Content that combines text, images, audio, video and animation in a single presentation. On web pages, such files are compressed and embedded with elements such as audio and video.