UGC NET Computer Science PYQ, December 2015 (Paper II & III, Selected Questions)

Explanation

Recursion does not offer better space or time complexity; it only makes the program compact and simpler to write and understand than a non-recursive implementation. The non-recursive version avoids function-call overhead and stack space.

Explanation

In-place sorts do not need extra space beyond the input array; any extra space they use is a constant, O(1).

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It is the responsibility of loader to transfer executable files from hard disk to main memory. Debugger is a computer program that is used to test and debug other-programs (target program). Compiler is a software which converts a program written in high level language (Source Language) to low level language. Linker takes object files, links them with each other and with any library files that you specify and produces an executable output file.

Explanation

Initially term = 1, sum = 0. Iteration 1 (i = 1): term = 1 * x/1 = x; sum = x Iteration 2 (i = 2): term = x * x/2 = x²/2; sum = x + x²/2 Iteration 3 (i = 3): term = (x²/2) * x/3 = x³/6; sum = x + x²/2 + x³/6 Iteration 4 (i = 4): term = (x³/6) * x/4 = x⁴/24; sum = x + x²/2 + x³/6 + x⁴/24 This is x/1! + x²/2! + x³/3! + x⁴/4! + ....

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Inheritance provides for code reuse, and public inheritance creates a subtype: a publicly derived class is a subtype of its base class. Both statements are correct.

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System calls are invoked from user mode by a software interrupt (trap). A privileged instruction cannot be the answer because privileged instructions cannot be executed in user mode.

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The gettydefs file supplies the getty command with information about various terminal attributes, such as the default initialization and the login message. (i) There is nothing like contrab in Unix. (ii) The inittab file controls what happens whenever a Unix system is rebooted or forced to change run levels. (iii) init (short for initialization) is the first process started during booting of the computer system.

Explanation

Four views regarding the design of a data warehouse: Top-down view – allows selection of the relevant information necessary for the data warehouse; Data source view – exposes the information being captured, stored and managed by operational systems; Data warehouse view – consists of fact tables and dimension tables; Business query view – sees the data in the warehouse from the view of the end-user.

Explanation

Indexes are special lookup tables that the database search engine can use to speed up data retrieval. An index is a pointer to data in a table, very similar to an index at the back of a book.

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The LIKE operator with the % wildcard matches any sequence of characters: Select * from customers where city like '%GAR%';

Explanation

Services provided by a wireless access point in 802.11 WLAN: (i) Integration (ii) Disassociation (iii) Association (iv) Authentication (v) Privacy (vi) Distribution (vii) MSDU delivery. Error correction is not provided by the wireless access point in 802.11 WLAN.

Explanation

Flow control is a function of the data link layer and transport layer, not a network layer congestion policy. Flow control manages the rate of data transmission between two nodes to prevent a fast sender from overwhelming a slow receiver. Network layer congestion policies are: (1) Virtual circuits vs datagram inside the subnet (2) Packet queueing and service policy (3) Packet discard policy (4) Routing algorithm (5) Packet lifetime management.

Explanation

Identification, Flags and Fragment offset are the IPv4 header fields used for fragmentation. Type of service is not related to fragmentation.

Explanation

Prototyping and iterative are well-known software process models. In the timeboxing model, development is done iteratively as in the iterative enhancement model, with each iteration done in a timebox of fixed duration. Glass boxing is a software testing approach, not a process model.

Explanation

OLAP (Online Analytical Processing) is market oriented and used for data analysis by knowledge workers. It is characterized by a relatively low volume of transactions; queries are often very complex and involve aggregations; response time is an effectiveness measure; OLAP applications are widely used by data mining techniques.

Explanation

Electronic Banking or E-banking is the use of electronic means to transfer funds directly from one account to another instead of using physical methods like cash or cheques. It includes service like online banking and mobile banking.

Explanation

1 character = 1 byte and a 32-bit word = 4 bytes. At 4800 characters per second, one word is assembled every 1/1200 sec, so 1200 words are transferred per second by cycle stealing. The CPU executes 1 million instructions per second, so the slowdown = (1200/1000000) × 100 = 0.12%.

Explanation

A CPU handles interrupt by executing interrupt service subroutine by checking the interrupt register after finishing the executing of the current instruction.

Explanation

Priority of hardware interrupts in 8085: TRAP > RST 7.5 > RST 6.5 > RST 5.5 > INTR. INTR is a level-triggered, maskable interrupt and has the lowest priority.

Explanation

Consider k buckets. For each digit: (1) place each number in the appropriate bin – O(n); (2) append all the k bins sequentially – O(k). With d digits, the total is O(d(n + k)).

Explanation

The Floyd–Warshall algorithm uses dynamic programming and compares all possible paths through the graph between each pair of vertices. It does this with Θ(|V|³) comparisons.

Explanation

A feasible solution to an LP problem which is also a basic solution is called a basic feasible solution. A basic feasible solution is called degenerate if the value of at least one basic variable is zero. So the answer is option (a).

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An interface is an empty shell: there are only the signatures of the methods, which do not have a body, so statement (2) is true. A class can extend only a single class, whereas it can implement multiple interfaces, so statement (1) is true.

Explanation

To make a class abstract, at least one member function should be made a pure virtual function.

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In an OS, an indivisible (atomic) operation is performed entirely or not performed at all. This means the processor cannot be pre-empted during it.

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A memory management unit (MMU), sometimes called paged memory management unit (PMMU), is a hardware unit through which all memory references pass, primarily performing the translation of virtual memory addresses to physical addresses.

Explanation

In 1 msec (10⁶ nsec) there are 32 refresh cycles, each taking 100 nsec, so refresh time per msec = 32 × 100 = 3200 nsec. Equivalently, per memory cycle of 250 nsec, refresh cycles = (32 × 250)/10⁶ and refresh time = ((32 × 250)/10⁶) × 100 = 0.8 nsec; percentage = (0.8/250) × 100 = 0.32%.

Explanation

Windows 2000 uses the 16-bit UNICODE character set. Extended ASCII encodings are 8-bit or larger encodings that include the 7-bit ASCII characters.

Explanation

All three commands enable execute permission: X stands for execute and + adds the permission; ugo means user, group and others; a means all; with no class given, + applies it for all.

Explanation

rm chap* would remove all files beginning with chap. To remove a file whose name contains a special character, escape it with the backslash (\); this is called escaping or despecializing. So rm chap0\[1 – 3\] removes the file named chap0[1 – 3] itself.

Explanation

In the Unix file system, six types of file are distinguished: special, named pipes, links, symbolic links, regular (ordinary) and directory. A special file contains no data, but provides a mechanism to map physical devices to file names. The file names are used to access peripheral devices, such as terminals and printers.

Explanation

The following statements are true: (1) the ability to develop more realistic models of the real world; (2) the ability to represent the world in a non-geometric way; (3) the ability to develop databases using natural language approaches. Hence the answer is (a).

Explanation

Attribute 'one' can have 10 values from 1 to 10 and attribute 'two' can have 5 values from 1 to 5. Since 'two' is unique, it cannot repeat, and every tuple must have a distinct value of 'two' from only 5 possibilities. So the relation can have at most 5 tuples.

Explanation

R.B = S.B holds for 2 records (B = 2 and B = 4), so SQ2 (inner join) returns 2 tuples. The full outer join returns the 2 matching tuples plus the unmatched tuple of R (1, 3) and the unmatched tuple of S (7, 8), so SQ1 returns 4 tuples.

Explanation

Query (3) returns the union of the two result sets, so it returns between 10 and 17 rows. If all rows are distinct the answer would be 10 + 7 = 17; if set (2) is a subset of set (1), it is 10 + 7 – 7 = 10. Among the options only 10 is possible.

Explanation

A socket address is the combination of an IP address & a port number, much like one end of a telephone connection is the combination of a phone number and a particular extension.

Explanation

With eight clusters, each containing 9 regions of 10 routers, each router needs 10 entries for local routers, 8 entries for the other regions in its own cluster and 7 entries for the distant clusters: total 10 + 8 + 7 = 25.

Explanation

A host number of 0 denotes the network address of a network. Addresses with a network number of 0 refer to the current network, allowing a host to send to a neighbour without needing to know the network number of its local network (IP packets with destination network address 0 are not routed).

Explanation

Multipurpose Internet Mail Extensions (MIME) is an internet standard that extends the format of email to support text in character sets other than ASCII, non-text attachments (audio, video, images, application programs etc.) and message bodies with multiple parts.

Explanation

Requirement validation is an activity in the requirements phase where the gathered requirements are checked for completeness, consistency and correctness. Prototyping is a technique for requirement analysis that builds a working model to get user feedback. Function points are a commonly used size metric for requirements. The modeling-oriented approach is not one of the methods for specifying the functional specifications, so statement (c) is incorrect.

Explanation

Usability is not highly affected by the architecture of the software; performance, reliability and portability are highly affected by the software architecture.

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The <SCRIPT> tag is an extension to HTML that can enclose any number of JavaScript statements. Syntax: <script> ... </script>

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Statement (2) and Statement (3) are not true because JavaScript is not stripped down version of Java and they are not originated from Island of Java. Although they are different languages, JavaScript's syntax is loosely based on Java.

Explanation

XML data is described using a DTD (or schema) and description nodes; XSL is used to transform/present XML, not to describe it. The correct statements are (1) and (3). Hence the answer is option (d).

Explanation

In image processing, blind deconvolution is a deconvolution technique that permits recovery of the target scene from a single or a set of blurred images in the presence of a poorly determined or unknown point spread function (PSF). It combines blur identification and image restoration.

Explanation

A pixel is a point of light, one tiny dot on a raster display; though it has no structure, it is a building block and a graphics primitive. Lines, especially straight lines, constitute the basic building block of line graphs, bar and pie charts, graphs of mathematical functions, engineering drawings and architectural plans. Points and lines are the basic building blocks of computer graphics.

Explanation

In a constraint satisfaction problem (e.g. the map colouring problem), constraints are expressed as arithmetic equations and inequalities that bind (restrict) the values of the variables. So option (a) is the proper choice.