Maharashtra HSC Computer Science (Bifocal) key terms

Base-2 positional numeral system that uses only the digits 0 and 1, where each place value is a power of two. Computers rely on it because two-state electronic circuits map directly onto these two symbols.

Single binary digit, either 0 or 1, and the smallest unit of data a computer handles. Eight bits make one byte, which usually stores one character, while four bits form a nibble.

Electronic circuit that performs a Boolean operation on one or more binary inputs and produces a single output. AND, OR, and NOT are the basic types; NAND, NOR, and XOR are derived from them.

Table that lists every possible combination of input values for a logic circuit next to the resulting output, so its behaviour can be checked. Two inputs need four rows; three inputs need eight.

Non-volatile memory whose contents are written during manufacture or by special equipment and afterwards can normally only be read. It holds the bootstrap loader and firmware, letting the computer start before an operating system is loaded.

Small, very fast memory placed between the processor and main memory that holds recently used instructions and data. It shortens average access time; levels L1, L2, and L3 differ in size and speed.

System software that manages hardware resources and provides services to application programs. It handles process scheduling, memory allocation, file systems, and device input/output, and offers the user an interface such as a desktop or command line.

Start-up process in which the computer loads the operating system into main memory. The bootstrap loader in ROM runs first, performs the power-on self-test, and then hands control to the operating system kernel.

Named collection of related data stored on secondary storage and treated as one unit by the operating system. Files carry extensions such as .txt or .cpp that indicate their format and the program that can open them.

Logical container that groups files and subdirectories into a hierarchy, letting users organise data, avoid duplicate names, and set paths such as C:\work\notes.txt. It is also called a folder.

Finite, ordered set of unambiguous steps that solves a problem or completes a task. A valid algorithm is definite, effective, and guaranteed to terminate, and it can be written as pseudocode or a flowchart.

Diagram that shows an algorithm using standard symbols: an oval for start and stop, a parallelogram for input and output, a rectangle for processing, a diamond for decisions, and arrows for the sequence of control.

Translator that converts a complete source program into machine code before it runs, reporting syntax errors for the whole program at once. The resulting object code executes without the compiler and is usually faster than interpreted code.

Translator that reads source code one statement at a time, converts it, and executes it immediately, stopping at the first error it finds. It needs no separate compilation step but generally runs slower than compiled code.

Named storage location in memory whose value can change while a program runs. In C and C++ each variable has a declared data type that fixes how much memory it occupies and which operations are allowed.

Control structure that repeats a block of statements while a condition remains true or for a fixed number of iterations. C and C++ provide for, while, and do-while loops; do-while tests its condition after running the body.

Named block of code that performs a specific job and can be called repeatedly from elsewhere in the program. Parameters carry data into it, and the return statement sends a value back to the caller.

Collection of elements of the same data type kept in consecutive memory locations and accessed by one name plus an index. The index usually starts at zero, and the size is fixed when the array is declared.

Linear data structure that follows last-in, first-out order. Elements are pushed onto the top and popped from the top, so the most recently inserted item leaves first; typical uses include function calls and expression evaluation.

Linear data structure that follows first-in, first-out order. Insertion takes place at the rear and deletion at the front, making it suitable for printer jobs, process scheduling, and breadth-first traversal.

Chain of nodes in which each node stores data plus a pointer to the next node. Unlike an array it can grow or shrink at run time and needs no contiguous memory, but reaching an element requires traversal.

Search method that repeatedly halves a sorted array, comparing the target with the middle element and discarding the half that cannot contain it. It is much faster than linear search but requires sorted data.

Variable that holds the memory address of another variable instead of a data value. In C and C++ the asterisk declares a pointer and the ampersand supplies an address; pointers underpin linked lists and dynamic memory.

Software that stores, retrieves, and manages structured data while controlling redundancy, concurrent access, and user permissions. It separates data from programs through a schema and answers queries written in a language such as SQL.

Column, or smallest set of columns, whose values uniquely identify every row in a table. It cannot hold nulls and must be unique; other tables may refer to it through foreign keys.

Column in one table that holds values matching the primary key of another table, linking the two and enforcing referential integrity. Its values may repeat and are allowed to be null unless the design forbids it.

Process of structuring tables to reduce duplicated data and prevent insertion, update, and deletion anomalies. It proceeds through normal forms; the first three remove repeating groups, partial dependencies, and transitive dependencies.

Standard language for defining, manipulating, and querying relational databases. Its statements are grouped into DDL for creating and altering tables, DML for inserting, updating, and deleting rows, and DQL for SELECT queries.

Arrangement of computers and links within a network. Common layouts are bus, star, ring, mesh, and tree, and the choice affects cost, fault tolerance, and how easily new nodes can be added.

Numeric label assigned to each device on a network so that data can be routed to it. IPv4 uses 32 bits written as four decimal octets; IPv6 uses 128 bits written as hexadecimal groups.

Agreed set of rules governing how data is formatted, addressed, transmitted, and acknowledged between devices on a network. TCP/IP, HTTP, FTP, and SMTP are familiar examples of such rules.

Application-layer protocol through which browsers and web servers exchange requests and responses. A request names a method such as GET or POST and a URL, while the response carries a status code and content.

Markup language used to write web pages, with tags describing headings, paragraphs, links, lists, tables, and forms. The browser reads these tags and renders the formatted page for the user.

Name-value pair written inside a start tag, such as href in an anchor or src in an image tag, that changes how the element behaves or displays. Attributes never appear as visible body text.

Clickable reference built with the anchor tag and an href attribute that takes the user to another page, a section of a page, an email address, or a file. Hyperlinks connect documents across the web.

Collection of input controls wrapped in the form tag that gathers data from a visitor and sends it to a server. The action attribute names the receiving script and the method attribute chooses GET or POST.

Structured sequence of phases followed to build an information system: requirement gathering, analysis, design, coding, testing, deployment, and maintenance. It gives a project checkpoints and makes cost and progress easier to control.

Linear SDLC model in which each phase is completed before the next begins, and changes are difficult once a phase is approved. It suits stable, well-understood requirements but delivers working software late.

Early investigation that decides whether a proposed system is worth building. It examines technical, economic, operational, and legal viability, and its report helps management approve, revise, or reject the project.

Testing that isolates and exercises individual functions or modules to confirm each behaves as designed. Programmers usually do it during coding, before integration testing, where the modules are combined and tested together.