Bhutan Civil Service Main Examination (ICT Category) key terms

A kernel data structure holding everything the operating system must know about a process: identifier, state, register contents, memory map, open files, and scheduling priority. It is saved and restored during context switches.

The act of saving the state of one running process or thread and loading the saved state of another so it can run. It costs time and does no useful user work, so excessive switching degrades throughput.

A technique giving each process an illusion of a large contiguous address space, with pages loaded from disk on demand and translated to physical frames by the memory management unit using page tables.

An interrupt raised when a program accesses a page not currently resident in physical memory. The operating system must fetch the page from secondary storage, possibly evicting another page first.

A collapse in performance where the system spends most of its time swapping pages in and out rather than executing instructions, usually because too many processes compete for too little physical memory.

A situation where a set of processes each wait indefinitely for a resource held by another in the set. It requires mutual exclusion, hold-and-wait, no preemption, and circular wait to occur simultaneously.

A synchronisation primitive consisting of an integer and a queue, manipulated only by atomic wait and signal operations, used to enforce mutual exclusion or to signal that an event has occurred between cooperating processes.

A defect in which the correctness of a program depends on the unpredictable timing or interleaving of concurrent operations on shared data, so results vary between runs even with identical inputs.

A notation describing how an algorithm's running time grows with input size, ignoring constants and lower-order terms. For example, binary search is O(log n) while linear search is O(n).

A linear data structure with last-in-first-out access, where insertion and removal both occur at one end. It underpins function call management, expression evaluation, and depth-first traversal.

A linear data structure with first-in-first-out access, where items are added at the rear and removed from the front. Variants include circular, priority, and double-ended queues used in scheduling and buffering.

A structure mapping keys to values through a hash function that computes an index into an array, giving average constant-time lookup but requiring collision handling by chaining or open addressing.

A technique where a function calls itself on a smaller version of the same problem, requiring a base case to stop and relying on the call stack to hold intermediate state.

The stepwise process of organising relational tables to remove redundancy and update anomalies, progressing through forms such as 1NF, 2NF, 3NF and BCNF by eliminating partial and transitive dependencies.

A column or minimal set of columns whose values uniquely identify each row in a table and can never be null. Other tables reference it through foreign keys to enforce referential integrity.

The four guarantees of a reliable transaction: atomicity (all or nothing), consistency (valid state to valid state), isolation (concurrent transactions do not interfere), and durability (committed changes survive failure).

An auxiliary data structure, commonly a B-tree, that lets the database locate rows without scanning the whole table, speeding reads at the cost of extra storage and slower writes.

A 32-bit pattern that separates the network portion of an IPv4 address from the host portion, allowing devices to decide whether a destination is local or must be reached through a router.

A compact way of writing an IP network as an address followed by a slash and the number of leading network bits, such as 192.168.10.0/24, which supports variable-length subnetting and route aggregation.

A set of rules by which routers exchange reachability information and compute forwarding tables. Interior examples include OSPF and RIP; BGP carries routes between autonomous systems on the internet.

A hierarchical, distributed naming service that translates human-readable domain names into IP addresses through recursive resolvers and authoritative servers, using cached records with time-to-live values.

A cryptographic protocol layered above TCP that authenticates a server with certificates and negotiates keys to encrypt traffic, providing confidentiality and integrity for web and other application protocols.

The policies, hardware, and trusted authorities that issue, distribute, and revoke digital certificates binding public keys to identities, enabling authentication and secure key exchange at scale.

A social-engineering attack that impersonates a trusted party through email, messages, or fake websites to trick users into revealing credentials, transferring money, or installing malicious software.

An access control approach requiring two or more independent evidence types, such as a password plus a one-time code or hardware token, so a stolen password alone is insufficient to gain entry.

The security rule that each user, process, or service should hold only the minimum permissions needed for its task, limiting the damage that a compromised account or faulty program can cause.

A documented set of procedures enabling an organisation to keep critical services running or restore them quickly after disruption, covering backups, alternate sites, staff roles, and tested recovery targets.

The structured phases through which software passes, typically requirements gathering, analysis, design, implementation, testing, deployment, and maintenance, with models such as waterfall and iterative arranging them differently.

An iterative, incremental approach delivering working software in short cycles with continuous customer feedback, favouring adaptability over exhaustive up-front specification and heavy documentation.

A behavioural UML diagram showing external actors, the system boundary, and the services the system provides, used early in analysis to clarify scope and user goals.

A table linking each requirement to its design elements, code modules, and test cases, so that coverage can be verified and the impact of any change assessed.

A formal contract between a service provider and a customer defining measurable performance targets such as uptime, response time, and support response, together with remedies for missing them.

An architectural style for web services in which clients manipulate resources identified by URLs using standard HTTP methods, with stateless requests and representations typically exchanged as JSON.

A defined contract through which one software component requests services from another, specifying available operations, input formats, output formats, and error behaviour without exposing internal implementation.

A design approach using flexible grids, fluid images, and media queries so that a single website adapts its layout sensibly across phones, tablets, and desktop screens without separate sites.

A web application built with modern browser features, including a service worker and manifest, so it can be installed on a device, work offline, and send notifications while remaining delivered over the web.

On-demand delivery of computing resources over a network with self-service provisioning, pooled capacity, rapid elasticity, and measured pay-per-use billing, offered as infrastructure, platform, or software services.

Networks of physical devices embedded with sensors, actuators, and network connectivity that collect and exchange data, enabling remote monitoring and automation but widening the attack surface.

Processing very large, fast-moving, varied datasets with distributed tools to uncover patterns and support decisions, typically described by the volume, velocity, variety, and veracity of the data.

A cryptographic value computed over a message with a sender's private key and verified with the public key, proving origin and detecting any alteration of the content in transit.

A national set of standards, data definitions, and architectural guidelines enabling government agencies to share information and reuse systems, avoiding duplicated silos and enabling joined-up online services.

Bhutan's development philosophy, articulated from the 1970s, holding that public policy should balance equitable socio-economic development with environmental conservation, cultural preservation, and good governance.

The Bhutanese regulator established under the Information, Communications and Media Act, responsible for licensing and overseeing telecommunications, broadcasting, and media services in the kingdom.

Money or effort already spent that cannot be recovered, and which should therefore be ignored when deciding whether to continue a project; only future costs and benefits are relevant.

A measure of how widely values in a dataset spread around their mean, calculated as the square root of the average squared deviation, expressed in the same units as the data.