Computer Science Previous Year Questions (page 29)

Explanation

Diligence means a computer can work for long hours with the same accuracy, without tiredness or loss of concentration.

Explanation

Pico means 10⁻¹², so 1 picosecond = 10⁻¹² s. 10⁻⁹ is nano and 10⁻¹⁵ is femto.

Explanation

I: 1071 = 2×512 + 0×64 + 5×8 + 7 = (2057)₈, correct. II: (1AF)₁₆ = 256 + 160 + 15 = 431, not 413, so only I is correct.

Explanation

Base 7 uses digits 0-6, so the largest four-digit number is 6666 (7777 is invalid). The smallest four-digit base-8 number is 1000, not 1111. Neither statement is correct.

Explanation

A transistor is a semiconductor device used as an electronically controlled switch or amplifier, and is the basic element of digital circuits.

Explanation

A compiler is system software that translates a high-level language program into machine language (object code) as a whole.

Explanation

Binary search needs at most ⌊log₂n⌋ + 1 comparisons. 2¹³ = 8192 ≤ 12000 < 16384 = 2¹⁴, so ⌊log₂12000⌋ = 13 and the maximum is 14.

Explanation

In the worst case (reverse-sorted input) bubble sort makes n(n−1)/2 comparisons and swaps, so it is O(x²) with x elements.

Explanation

main() is called by the system, but its body is written by the programmer, so it is treated as a user-defined function, not a library (pre-defined) function.

Explanation

cgets() (from conio.h) reads a string from the console. puts() writes a string, and getche()/getchar() read single characters.

Explanation

62 is decimal, 062 is octal = 6×8 + 2 = 50, and 0x62 is hexadecimal = 6×16 + 2 = 98. With no separators, the output is 625098.

Explanation

Bubble sort makes one swap per inversion. In S O R T E D (order D < E < O < R < S < T), the inversions are S:4, O:2, R:2, T:2, E:1, totalling 11 interchanges.

Explanation

Right-left-node is the exact reverse of preorder (node-left-right). The preorder is A, B, C, D, E, F, G, H, I, J, K, so the new-order is K, J, I, H, G, F, E, D, C, B, A.

Explanation

j takes the values 1, 2, 4, ... while j ≤ n, so the loop condition is checked about log₂n + 1 times, which is the keyed answer. Strictly, the final failing test makes it ⌊log₂n⌋ + 2.

Explanation

A DBMS is software for creating, managing, maintaining and retrieving data stored in a database (e.g. MySQL, Oracle).

Explanation

A MAN covers a city by connecting many LANs, and it can carry both data and voice. Both statements are correct.

Explanation

A multiplexer combines many low-speed input lines into one high-speed line (shared channel). A demultiplexer does the reverse.

Explanation

Star and bus are network topologies (along with ring, mesh, tree). There is no "car topology", so only I and II are correct.

Explanation

The transmission modes are simplex, half duplex and full duplex. "Half simplex" does not exist, so I and III are correct.

Explanation

A dot-matrix printer forms characters by pins striking an inked ribbon against paper, so it is an impact printer. Inkjet, laser and thermal printers are non-impact.

Explanation

Speech recognition converts spoken words into computer input or text. Speaker recognition only identifies who is speaking.

Explanation

Coulomb's law: F = k·q₁q₂/r², so the force is directly proportional to the product of the charges and inversely proportional to the square of the distance.

Explanation

1 + A = 1, and (A + B)(A' + B) = B + AA' = B. So the expression simplifies to B.

Explanation

NOR-ing each input with itself gives A' and B' (2 gates). A third NOR gives (A' + B')' = AB. So 3 NOR gates are needed.

Explanation

The crossing must close if any one or more of the 4 tracks has a train, i.e. output 1 when at least one input is 1, which is the OR function.

Explanation

m0 (000) and m2 (010) group to A'C'. m5 (101) and m7 (111) group to AC. So f = A'C' + AC.

Explanation

An astable multivibrator is free running (no stable state), and a bistable multivibrator is the flip-flop. Both pairs are swapped, so neither is correct.

Explanation

Multiplexers can implement any logic function directly, which simplifies design, reduces the IC package count and removes the need to minimise the expression. All three are advantages.

Explanation

The first two factors are 1. (A + B + C)(A' + B' + C') is 0 only when A, B, C are all equal, which is what AB' + B'C + A'B + A'C + AC' + BC', i.e. option B, expresses.

Explanation

Key attributes of good information include accuracy, timeliness, relevance, completeness. Isolation is not an attribute of information.

Explanation

DASD stands for Direct Access Storage Device, such as a magnetic disk, where any record can be accessed directly.

Explanation

In a sequential file, inserting or deleting a record needs the whole file to be read and rewritten, and locating a record needs on average half the records to be scanned. Both are correct.

Explanation

Volatility measures how often records are added or deleted. Frequent additions and deletions mean high volatility.

Explanation

An entity is described by its attribute values. For example, a student entity is described by values of roll number, name and class.

Explanation

REAL, INTERVAL and TIMESTAMP are SQL data types. BASE is not an SQL data type.

Explanation

A truth table lists the output for every combination of binary inputs, giving the input-output relation of a gate in tabular form.

Explanation

Boolean algebra expresses the input-output relation of logic diagrams algebraically, which makes analysing and designing digital circuits easier. Both statements are correct.

Explanation

By De Morgan's theorem (x + y)' = x'·y', i.e. x'y'.

Explanation

A NOR gate can be drawn as an OR symbol with an output bubble, or, by De Morgan's law (A + B)' = A'B', as an AND symbol with bubbles on both inputs. Both represent NOR.

Explanation

A callback function is passed as an argument to another function and called back inside it, e.g. in setTimeout or event handlers.

Explanation

AJAX stands for Asynchronous JavaScript and XML: it updates parts of a page by exchanging data with the server in the background.

Explanation

A provision is a charge against profit made for a known liability or loss, while a reserve is an appropriation of profit kept aside for future needs. Both statements are correct.

Explanation

Permanent (real and personal) accounts are balanced and carried forward to the next period, while temporary (nominal) accounts are closed by transfer to the profit and loss account. Both are correct.

Explanation

White-box testing is also called glass-box (or clear-box) testing because the tester can see the internal code and logic.

Explanation

SQA stands for Software Quality Assurance: activities that make sure software processes and products meet quality standards.

Explanation

The spiral model develops software in a series of evolutionary releases, one per loop. A sequential (waterfall) model delivers the product only once at the end.

Explanation

Logical cohesion groups elements that do logically similar operations, such as all error handling or all data input routines. B describes functional cohesion and C procedural cohesion.

Explanation

Common coupling occurs when modules share the same global data area. Communicating through elementary data items is data coupling, and through composite data is stamp coupling.

Explanation

A Gantt chart can be derived automatically from a PERT chart, but a PERT chart cannot be derived from a Gantt chart because Gantt charts lack task dependencies. Both statements are false.

Explanation

The Java compiler (javac) translates source code into platform-independent bytecode (.class files), which the JVM then executes.