Computer Science Previous Year Questions (page 5)

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Floyd-Warshall runs three nested loops over k, i and j, each from 1 to n, so it takes O(n³) time.

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The divide-and-conquer MaxMin algorithm makes about 3n/2 - 2 comparisons; T(n) = 2T(n/2) + 2 solves to O(n).

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By the principle of optimality, a minimum-cost path through a multistage graph is built from minimum-cost sub-paths, so the shortest path is the one with the lowest total cost.

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Integer is a primitive (built-in) data type, while stack, queue and list are abstract data types defined by their operations, independent of implementation.

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Inserting at the beginning needs only to set newnode->next = head and head = newnode, which is O(1); inserting at the end or at a position requires traversal.

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Compressed sparse formats store only non-zero values with their indices; CSC compresses the data column by column, so it suits sparse matrices and column-wise access. CSR is the row-wise counterpart.

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CSR stores the non-zeros row by row with a row-pointer array, so all elements of a row are contiguous and can be traversed efficiently.

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An image is a grid of pixels addressed by row and column, so a 2-D array (one value per pixel, e.g. grayscale) is the natural structure.

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In row-major order the rows are stored one after another, so element (i, j) is at B + (i × n + j) for n columns (times the element size, taken as 1 here).

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The Banker's algorithm checks before each allocation whether the system stays in a safe state, so it avoids deadlock rather than detecting or preventing it.

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Multilevel queue scheduling places processes in separate queues by priority class and serves higher-priority queues first, so it is built directly on priority scheduling.

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In deadlock detection, allocation and request matrices record which resources each process holds and requests, i.e. they represent resource allocation.

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A race condition occurs when processes access shared data concurrently and the result depends on the order of access, i.e. they compete for shared resources.

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Users' typed commands cannot be executed by the hardware as they are; the command interpreter (shell) reads each command and translates it into system calls and programs the machine can run.

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One-to-many means one entity instance is linked to many instances of another, e.g. one teacher teaching many classes.

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A report generator takes data from files or databases and formats it into printed reports; it does not update files.

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A master file holds relatively permanent core data (e.g. customer or employee records) that is kept and updated over time, so it is called a perpetual file.

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HTTP is the application-layer protocol for transferring web pages between browsers and web servers, i.e. web browsing; email uses SMTP and file transfer FTP.

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ISO 9000 and SEI CMM are quality frameworks: ISO 9000 sets quality management standards, and CMM rates and improves the maturity of software processes.

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Perfective maintenance adds new features or improves performance in response to user needs; corrective fixes bugs and adaptive suits a new environment.

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ISO 9000 is a family of quality management standards that gives guidelines for producing software of consistent, high quality.

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Reverse engineering analyses existing software to recover and document its design, structure and functionality, often when documentation is missing.

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Overloading means several methods in the same class share a name but have different parameter lists; overriding redefines an inherited method with the same signature.

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Namespaces group related classes and functions under a name, organising code logically and avoiding name clashes.

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Creating a new class from an existing one is derivation (inheritance); the new class is a derived class or subclass.

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An exception is a runtime event (e.g. divide by zero) that disrupts the normal flow of instructions and can be caught and handled.

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A DTD defines the legal structure of an XML document: which elements and attributes are allowed, their order and nesting, so the document can be validated.

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PHP is a recursive acronym for "PHP: Hypertext Preprocessor" (originally "Personal Home Page").

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In PHP a single-line comment starts with // (or #); /* */ is a multi-line comment and <!-- --> is HTML.

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DROP TABLE removes the table structure and its data from the database; DELETE removes only rows.

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In Chomsky normal form every production is A → BC (two variables) or A → a (a single terminal).

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Every rule adds one 0 and one 1 together (0S1, 1S0) or concatenates such strings (SS), so all generated strings have equal numbers of 0s and 1s.

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Recursively enumerable languages are Type 0 in the Chomsky hierarchy, generated by unrestricted grammars and recognised by Turing machines.

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A universal Turing machine takes the description of any other TM and its input and simulates it, so it is a reprogrammable (stored-program) Turing machine.

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Industry 4.0, the fourth industrial revolution, is defined by IoT, real-time data and cyber-physical systems in manufacturing.

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The Modbus serial line specification makes 19200 bps the required default baud rate for Modbus RTU devices (9600 is also commonly supported).

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iDisk was the online storage drive in Apple's MobileMe, where files could be browsed and shared; "iDesk" in the option refers to it.

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A frame (Minsky) is a structure of slots and values describing a stereotyped object or situation, a method of knowledge representation in AI.

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Hyponymy is the "is-a-kind-of" relation: A is a hyponym of B when A is subordinate to B (rose is a hyponym of flower). Part-whole is meronymy.

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WordNet is a lexical database linking words by relations such as synonymy and hyponymy, a classic large semantic network.

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Turing showed that a simple machine manipulating symbols (such as 0 and 1, a binary system) can carry out any algorithmic task.

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Expert systems are expected to be reliable, understandable, highly responsive and high-performing, so "unreliable" is not a characteristic.

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Expert systems can advise, explain and suggest alternative solutions, but they cannot possess human abilities, refine their own knowledge or replace human decision makers.

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JESS is the Java Expert System Shell, a rule engine and expert-system shell written in Java.

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Secure e-commerce transactions need integrity (data not altered), confidentiality (data not disclosed) and overall security such as authentication, so all apply.

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Public key cryptography uses a pair of different keys (public and private), so it is asymmetric; symmetric cryptography uses one shared key.

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MMID (Mobile Money Identifier) is a 7-digit number issued by banks for IMPS mobile money transfers.

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Unwanted, unsolicited or unclassified email is called junk mail (also commonly called spam); the key uses "junk mail".

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Animation is a sequence of drawn images shown in quick succession to simulate motion of objects.