### Computer Science (GATE Exam) 2013 - Previous Question Paper Solution

Description: GATE Exam Previous Year Question Paper Solution Computer Science(CS) - 2013 | |

Number of Questions: 63 | |

Created by: Aliensbrain Bot | |

Tags: Computer Science GATE CS Previous Year Paper |

Consider an undirected random graph of eight vertices. The probability that there is an edge between a pair of vertices is ½. What is the expected number of unordered cycles of length three?

Which of the following statements is/are TRUE for undirected graphs? P: Number of odd degree vertices is even. Q: Sum of degrees of all vertices is even.

Which one of the following expressions does NOT represent exclusive NOR of x and y?

Which one of the following functions is continuous at x = 3?

In a k-way set associative cache, the cache is divided into v sets, each of which consists of k lines. The lines of a set are placed in sequence one after another. The lines in set s are sequenced before the lines in set (s+1). The main memory blocks are numbered from 0 onwards. The main memory block numbered j must be mapped to any one of the cache lines from

Which of the following statements are TRUE? (1) The problem of determining whether there exists a cycle in an undirected graph is in P. (2) The problem of determining whether there exists a cycle in an undirected graph is in NP. (3) If a problem A is NP-complete, there exists a non-deterministic polynomial time algorithm to solve A.

Which of the following statements is/are FALSE? (1) For every non-deterministic Turing machine, there exists an equivalent deterministic Turing machine. (2) Turing recognisable languages are closed under union and complementation. (3) Turing decidable languages are closed under intersection and complementation. (4) Turing recognisable languages are closed under union and intersection.

An index is clustered, if

The transport layer protocols used for real-time multimedia, file transfer, DNS and email respectively are

What is the time complexity of Bellman-Ford single-source shortest path algorithm on a complete graph of n vertices?

Assume that source S and destination D are connected through two intermediate routers labelled R. Determine how many times does each packet has to visit the network layer and the data link layer during a transmission from S to D.

Three concurrent processes X, Y and Z execute three different code segments that access and update certain shared variables. Process X executes the P operation (i.e. wait) on semaphores a, b and c; process Y executes the P operation on semaphores b, c and d; process Z executes the P operation on semaphores c, d, and a before entering the respective code segments. After completing the execution of its code segment, each process invokes the V operation (i.e. signal) on its three semaphores. All semaphores are binary semaphores initialised to one. Which one of the following represents a deadlock-free order of invoking the P operations by the processes?

Which one of the following is the tightest upper bound that represents the time complexity of inserting an object into a binary search tree of n nodes?

What is the maximum number of reduce moves that can be taken by a bottom-up parser for a grammar with no epsilon and unit-production (i.e. of type A $\rightarrow$$\in$ Î and A $\rightarrow$ a) to parse a string with n tokens?

Which one of the following is the tightest upper bound that represents the number of swaps required to sort n numbers using selection sort?

What is the worst case time complexity of a sequence of n queue operations on an initially empty queue?

Consider the languages L_{1} = $\phi$ and L_{2} = {a}. Which one of the following represents L_{1} ^{$L_2^$$UL_2^$}?

Using public key cryptography, X adds a digital signature $\sigma$to message M, encrypts <M, $\sigma$>, and sends it to Y, where it is decrypted. Which one of the following sequences of keys is used for the operations?

The smallest integer that can be represented by an 8-bit number in 2’s complement form is

Consider an instruction pipeline with five stages without any branch prediction.
Fetch Instruction (FI), Decode Instruction (DI), Fetch Operand (FO), Execute Instruction (EI) and Write Operand (WO). The stage delays for FI, DI, FO, EI and WO are 5 ns, 7 ns, 10 ns, 8 ns and 6 ns respectively. There are intermediate storage buffers after each stage and the delay of each buffer is 1 ns. A program consisting of 12 instructions I_{1}, I_{2}, I_{3}, ….. I_{12} is executed in this pipelined processor. Instruction I_{4} is the only branch instruction and its branch target is 9 I_{9}. If the branch is taken during the execution of this program, the time (in ns) needed to complete the program is

The preorder traversal sequence of a binary search tree is 30, 20, 10, 15, 25, 23, 39, 35, 42. Which one of the following is the postorder traversal sequence of the same tree?

What is the return value of f(p, p) if the value of p is initialised to 5 before the call? Note that the first parameter is passed by reference, whereas the second parameter is passed by value.

```
int f(int &x, int c) {
c = c – 1;
if (c == 0) return 1;
x = x + 1;
return f (x, c) * x;
}
```

Determine the maximum length of cable (in km) for transmitting data at a rate of 500 Mbps in an Ethernet LAN with frames of size 10,000 bits. Assume the signal speed in the cable to be 2,00,000 km/s.

Match the problem domains in Group I with the solution technologies in Group II.

Group I |
Group II |

(P) Services oriented computing | (1) Interoperability |

(Q) Heterogeneous communicating systems | (2) BPMN |

(R) Information representation | (3) Publish-find bind |

(S) Process description | (4) XML |

In an IPv4 datagram, the M bit is 0, the value of HLEN is 10, the value of total length is 400 and the fragment offset value is 300. The position of the datagram and the sequence numbers of the first and the last bytes of the payload respectively are

Which one of the following does NOT equal $\begin{vmatrix} 1& x & x^{2}\\ 1& y & y^{2}\\ 1& z & z^{2} \end{vmatrix}?$

Which of the following is/are undecidable?

- G is a CFG. Is L (G) = $\phi$?
- G is a CFG. IS L (G) = $\sum *$?
- M is a Turning machine. Is L (M) regular?
- A is a DFA and N is an NFA. Is L (A) = L (N)?

A RAM chip has a capacity of 1024 words of 8 bits each (1K × 8). The number of 2 × 4 decoders with enable line needed to construct a 16K × 16 RAM from 1K × 8 RAM is

Suppose p is the number of cars per minute passing through a certain road junction between 5 PM and 6 PM, and p has a Poisson's distribution with mean 3. What is the probability of observing fewer than 3 cars during any given minute in this interval?

A shared variable x, initialised to zero, is operated on by four concurrent processes W, X, Y and Z as follows: Each of the processes W and X reads x from memory, increments by one, stores it to memory and then terminates. Each of the processes Y and Z reads x from memory, decrements by two, stores it to memory and then terminates. Each process before reading x invokes the P operation (i.e. wait) on a counting semaphore S and invokes the V operation (i.e. signal) on the semaphore S after storing x to memory. Semaphore S is initialised to two. What is the maximum possible value of x after all processes complete execution?

Consider the following two sets of LR (1) items of an LR (1) grammar X $\rightarrow$ c. X c / d X $\rightarrow$ c.X, $ X $\rightarrow$ .Cx, c / d X $\rightarrow$.Cx, $ X $\rightarrow$ .d, c / d X $\rightarrow$.d, $ Which of the following statements related to merging of the two sets in the corresponding LALR parser is/are FALSE?

- Cannot be merged since look aheads are different
- Can be merged but will result in S–R conflict
- Can be merged but will result in R–R conflict
- Cannot be merged since goto on c will lead to two different sets

Function f(x) is known at the following points: x 0 0.3 0.6 0.9 1.2 1.5 1.8 2.1 2.4 2.7 3.0 f(x) 0 0.09 0.36 0.81 1.44 2.25 3.24 4.41 5.76 7.29 9.00

The value of ^{$\int_0^2 f$} (x) dx computed using the trapezoidal rule is

Consider the following relational schema.

Students(rollno: integer, sname: string) Courses(courseno: integer, cname: string) Registration(rollno: integer, courseno: integer, percent: real)

Which of the following queries are equivalent to this query in English?

“Find the distinct names of all students who score more than 90% in the course numbered 107”

(I)

```
SELECT DISTINCT S.sname
FROM Students as S, Registration as R
WHERE R.rollno=S.rollno AND R.courseno=107 AND R.percent >90
```

(II) $ \prod_{sname}(σ_{courseno=107 ∧ percent > 90} (Registration ⋈ Students)) $

(III) $\left\{T \mid ∃S \in Students, ∃R \in Registration ( S.rollno=R.rollno \land R.courseno=107 ∧ R.percent>90 ∧T.sname=S.sname)\right \}$

(IV) $\left\{ \langle S_N\rangle \mid ∃S_R∃R_P (\langle S_R,S_N\rangle ∈Students ∧ \ \langle S_R,107,R_P\rangle ∈Registration ∧ R_P>90) \right\}$

Consider the following languages:

L_{1} = {0^{p} 1 ^{q}_{0}^{r} | p, q, r ^{$\ge$} 0}
L_{2} = {0^{p}1^{q}0^{r} | p, p, r ^{$\ge$} 0, p ^{$\ne$ }r}

Which of the following statements is FALSE?

A binary operation ^{$\oplus$}on a set of integers is defined as x ^{$\oplus$}y = x^{2} + y^{2}. Which of the following is TRUE about ^{$\oplus$}?

Consider the following sequence of micro–operations: MBR$\leftarrow$ PC MAR $\leftarrow$X PC $\leftarrow$Y Memory MBR Which one of the following is a possible operation performed by this sequence?

The number of elements that can be sorted in $Θ(\log n)$ time using heap sort is

Consider the following function.

```
int unknown (int n) {
int i, j, k 0;
for i n / 2; i
```

The tester now tests the program on all input strings of length five consisting of characters ‘a’, ‘b’, ‘c’, ‘d’ and ‘e’ with duplicates allowed. If the tester carries out this testing with the four test cases given above, how many test cases will be able to capture the flaw?

What is the logical translation of the following statement?

“None of my friends is perfect.”

The line graph L(G) of a simple graph G is defined as follows: • There is exactly one vertex v(e) in L(G) for each edge e in G. • For any two edges e and e’ in G, L(G) has an edge between v(e) and v(e’), if and only if e and e’ are incident with the same vertex in G. Which of the following statements is/are TRUE? (P) The line graph of a cycle is a cycle. (Q) The line graph of a clique is a clique. (R) The line graph of a planar graph is planar. (S) The line graph of a tree is a tree.

Consider a hard disk with 16 recording surfaces (0 – 15) having 16384 cylinders (0 − 16383) and each cylinder contains 64 sectors (0 − 63). Data storage capacity in each sector is 512 bytes. Data are organised cylinder–wise and the addressing format is <cylinder no., sector no.>. A file of size 42797 KB is stored in the disk and the starting disk location of the file is <1200, 9, 40>. What is the cylinder number of the last sector of the file, if it is stored in a contiguous manner?

A certain computation generates two arrays a and b such that a [i] = f (i) for 0 $\le$ i < n and b [i] = g (a [i]) for 0 $\le$ i < n. Suppose this computation is decomposed into two concurrent processes X and Y such that X computes the array a and Y computes the array b. The processes employ two binary semaphores R and S, both initialised to zero. The array a is shared by the two processes. The structures of the processes are shown below.

```
Process X;
Process Y;
private i;
private i;
for (i = 0; i < n; i + +) {
for (i = 0; i < n; i + +) {
a [i] = f (i);
EntryY (R, S);
ExitX (R, S);
b [i] = g (a [i]);
}
}
```

Which one of the following represents the CORRECT implementations of ExitX and EntryY?

The following figure represents access graphs of two modules M1 and M2. The filled circles represent methods and the unfilled circles represent attributes. If method m is moved to module M2 keeping the attributes where they are, what can we say about the average cohesion and coupling between modules in the system of two modules?

Consider the DFA given below.

Which of the following are FALSE?

- Complement of L (A) is context–free.
- $ L(A) = L((11^
*0+0)(0 + 1)^*0^*1^*) $ - For the language accepted by A, A is the minimal DFA.
- A accepts all strings over {0, 1} of length at least 2.

** Direction:** The following code segment is executed on a processor which allows only register operands in its instructions. Each instruction can have almost two source operands and one destination operand. Assume that all variables are dead after this code segment.
c = a + b;
d = c * a;
e = c + a;
x = c * c;
if (x > a) {
y = a* a;
}
else {
d = d * d;
e = e * e;
}

Suppose the instruction set architecture of the processor has only two registers. The only allowed compiler optimisation is code motion, which moves statements from one place to another while preserving correctness. What is the minimum number of spills to memory in the compiled code?

** Direction:** The following code segment is executed on a processor which allows only register operands in its instructions. Each instruction can have almost two source operands and one destination operand. Assume that all variables are dead after this code segment.

```
c = a + b;
d = c * a;
e = c + a;
x = c * c;
if (x > a) {
y = a* a;
}
else {
d = d * d;
e = e * e;
}
```

What is the minimum number of registers needed in the instruction set architecture of the processor to compile this code segment without any spill to memory? Do not apply any optimisation other than optimising register allocation.

The procedure given below is required to find and replace certain characters inside an input character string supplied in array A. The characters to be replaced are supplied in array oldc, while their respective replacement characters are supplied in array newc. Array A has a fixed length of five characters, while arrays oldc and newc contain three characters each. However, the procedure is flawed.

```
void find_and_replace (char *A, char *oldc, char *newc) {
for (int i=0; i<5; i++)
for (int j=0; j<3; j++)
if (A[i] == oldc[j])
A[i] = newc[j];
}
```

The procedure is tested with the following four test cases. (1) oldc = “abc”, newc = “dab” (2) oldc = “cde”, newc = “bcd” (3) oldc = “bca”, newc = “cda” (4) oldc = “abc”, newc = “bac”

The tester now tests the program on all input strings of length five consisting of characters ‘a’, ‘b’, ‘c’, ‘d’ and ‘e’ with duplicates allowed. If the tester carries out this testing with the four test cases given above, how many test cases will be able to capture the flaw?

Relation R has eight attributes ABCDEFGH. Fields of R contain only atomic values. F = {CH $\leftarrow$ G, A $\rightarrow$ BC, B $\rightarrow$ CFH, E $\rightarrow$ A, F $\rightarrow$ EG} is a set of functional dependencies (FDs) so that F+ is exactly the set of FDs that hold for R.

How many candidate keys does the relation R have?

A computer uses 46–bit virtual address, 32–bit physical address and a three–level paged page table organisation. The page table base register stores the base address of the first–level table (T_{1}) which occupies exactly one page. Each entry of T_{1} stores the base address of a page of the second–level table (T_{2}). Each entry of T_{2} stores the base address of a page of the third–level table (T_{3}). Each entry of T_{3} stores a page table entry (PTE). The PTE is 32 bits in size. The processor used in the computer has a 1 MB 16 way set associative virtually indexed physically tagged cache. The cache block size is 64 bytes.

What is the size of a page in KB in this computer?

Out of all the 2-digit integers between 1 and 100, a number has to be selected at random. What is the probability that the selected number is not divisible by 7?

A tourist covers half of his journey by train at 60 km/hr, half of the remainder by bus at 30 km/hr and the rest by cycle at 10 km/hr. The average speed of the tourist in km/hr during his entire journey is

In the following truth table, V = 1 if and only if the input is valid.

Inputs |
Outputs |

--- | --- |

D_{0} |
D_{1} |

0 | 0 |

1 | 0 |

0 | 1 |

1 | X |

X | X |

What function does the truth table represent?

Relation R has eight attributes ABCDEFGH. Fields of R contain only atomic values. F = {CH $\rightarrow$ G, A $\rightarrow$ BC, B $\rightarrow$ CFH, E $\rightarrow$ A, F $\rightarrow$ EG} is a set of functional dependencies (FDs) so that F+ is exactly the set of FDs that hold for R.

The relation R is

__ Directions:__ Fill in the blank.
Were you a bird, you ___________ in the sky.

After several defeats in wars, Robert Bruce went in exile and wanted to commit suicide. Just before committing suicide, he came across a spider attempting tirelessly to have its net. Time and again, the spider failed but that did not deter it to refrain from making attempts. Such attempts by the spider made Bruce curious. Thus, Bruce started observing the near-impossible goal of the spider to have the net. Ultimately, the spider succeeded in having its net despite several failures. Such act of the spider encouraged Bruce not to commit suicide. And then, Bruce went back again and won many battles and the rest is history. Which one of the following assertions is best supported by the above information?

Complete the following sentence. Universalism is to particularism as diffuseness is to _______.

A computer uses 46–bit virtual address, 32–bit physical address, and a three–level paged page table organization. The page table base register stores the base address of the first–level table (T_{1}) which occupies exactly one page. Each entry of T_{1} stores the base address of a page of the second–level table (T_{2}). Each entry of T_{2} stores the base address of a page of the third–level table (T_{3}). Each entry of T_{3} stores a page table entry (PTE). The PTE is 32 bits in size. The processor used in the computer has a 1 MB 16 way set associative virtually indexed physically tagged cache. The cache block size is 64 bytes.

What is the minimum number of page colours needed to guarantee that no two synonyms map to different sets in the processor cache of this computer?

Choose the grammatically INCORRECT sentence from the given options.

The current erection cost of a structure is Rs. 13,200. If the labour wages per day increase by 1/5 of the current wages and the working hours decrease by 1/24 of the current period, then the new cost of erection in Rs. is

Which one of the following options is the closest in meaning to the word given below? Nadir

Which one of the following is NOT logically equivalent to $¬∃x(∀ y (α)∧∀z(β ))$?