CS and IT GATE 2017 Set-1 Questions with Answer

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Ques 14 Automata

If G is grammar with productions

S → SaS | aSb | bSa | SS | ∈

where S is the start variable, then which one of the following is not generated by G?

abab

aaab

abbaa

babba

Ques 15 Automata

Consider the following grammar over the alphabet {a,b,c} given below, S and T are non-terminals.

G1: S-->aSb|T
T--> cT|∈
G2: S-->bSa|T
T--> cT|∈

The language L1(G1) ∩ L2(G2).

Finite

Non-finite but regular

Context-free but not regular

Recursive but not context-free

Ques 16 Automata

Consider the following context-free grammar over the alphabet ∑ = {a, b, c} with S as the start symbol:

S → abScT | abcT
T → bT | b

Which of the following represents the language generated by the above grammar?

{(ab)ⁿ(cb)ⁿ | n >= 1 }

{(abⁿcb^m₁cb^m₂...cb^m_n | n, m1, m2, ....., mn >= 1 }

{(ab)ⁿ(cb^m)ⁿ | n >= 1 }

{(ab)ⁿ(cbⁿ)^m | m, n >= 1 }

Ques 17 Automata

Consider the following grammar

P→xQRS
Q→yz|z
R→ w|∈
S→y

Which is FOLLOW(Q)?

{R}

{w}

{w, y}

{w, ∉}

Ques 18 C Programming

The output of executing the following C program is ________.

# include<stdio.h>
int total(int v)
{
static int count = 0;
while (v) {
count += v & 1;
v >>= 1;
}
return count;
}
void main()
{
static int x = 0;
int i = 5;
for (; i> 0; i--) {
x = x + total(i);
}
printf (“%dn”, x) ;
}

a is the correct answer.

Ques 19 C Programming

Consider the following C program.

#include<stdio.h>
#include<string.h>
void printlength (char *s, char *t)
{
unsigned int c = 0;
int len = ((strlen (s) - strlen (t)) > c) ? strlen (s) : strlen (t);
printf("%dn", len);
}

void main()
{
char *x = "abc";
char *y = "defgh";
printlength(x, y);
}

Recall that strlen is defined in string.h as returning a value of type size_t, which is an unsigned int . The output of the program is _________.

3 is the correct answer.

Ques 20 C Programming

Consider the following two functions
void fun1(int n){
if(n == 0) return;
printf(“%d”, n);
fun2(n-2);
printf(“%d”, n);
}

void fun2(int n){
if(n == 0) return;
printf(“%d”, n);
fun1(++n);
printf(“%d”, n);
}

The output printed when fun1 (5) is called is

53423122233445

53423120112233

53423122132435

53423120213243

Ques 21 C Programming

Consider the C functions foo and bar given below:

int foo(int val)
{
int x = 0;
while (val > 0)
{
x = x + foo(val--);
}
return val;
}
int bar(int val)
{
int x = 0;
while (val > 0)
{
x = x + bar(val-1);
return val;
}
}

Invocations of foo(3) and bar(3) will result in:

Return of 6 and 6 respectively.

Infinite loop and abnormal termination respectively.

Abnomal termination and infinite loop respectively.

Both terminating abnormally.

Ques 22 C Programming

Consider the C code fragment given below.

typedef struct node
{
int data;
node* next ;
} node;
void join(node* m, node* n)
{
node* p = n;
while (p->next != NULL)
{
p = p->next;
}
p–>next = m;
}

Assuming that m and n point to valid NULL- terminated linked lists, invocation of join will

append list m to the end of list n for all inputs

either cause a null pointer dereference or append list m to the end of list n

cause a null pointer dereference for all inputs.

append list n to the end of list m for all inputs.

Ques 23 C Programming

Consider the C code fragment given below.

typedef struct node
{
int data;
node* next ;
} node;
void join(node* m, node* n)
{
node* p = n;
while (p->next != NULL)
{
p = p->next;
}
p–>next = m;
}

Assuming that m and n point to valid NULL- terminated linked lists, invocation of join will

append list m to the end of list n for all inputs

either cause a null pointer dereference or append list m to the end of list n

cause a null pointer dereference for all inputs.

append list n to the end of list m for all inputs.

Ques 24 C Programming

Consider the following C code:

#include<stdio.h>
int * assignval (int *x, int val)
{
*x = val;
return x;
}
int main()
{
int *x = malloc(sizeof(int));
if (NULL == x) return;
x = assignval(x, 0);
if(x)
{
x = (int*) malloc(sizeof (int));
if (NULL == x) return;
x = assignval (x, 10);
}
printf("%dn", *x);
free(x);
}

The code suffers from which one of the following problems:

compiler error as the return of malloc is not typecast appropriately.

compiler error because the comparison should be made as x==NULL and not as shown.

compiles successfully but execution may result in dangling pointer.

compiles successfully but execution may result in memory leak.

Ques 25 C Programming

Consider the C struct defines below:

struct data {
int marks [100] ;
char grade;
int cnumber;
};
struct data student;

The base address of student is available in register R1. The field student grade can be accessed efficiently using

Post-increment addressing mode. (R1)+

Pre-decrement addressing mode, -(R1)

Index addressing mode, X(R1), where X is an offset represented in 2’s complement 16-bit representation.

Ques 26 COA

Instruction execution in a processor is divided into 5 stages.
Instruction Fetch(IF), Instruction Decode (ID), Operand Fetch(OF), Execute(EX), and Write Back(WB),
These stages take 5,4,20, 10 and 3 nanoseconds (ns) respectively. A pipelined implementation of the processor requires buffering between each pair of consecutive stages with a delay of 2 ns. Two pipelined implementations of the processor are contemplated:

(i) a naïve pipeline implementation (NP) with 5 stages and
(ii) an efficient pipeline (EP) where the OF stage id divided into stages OF1 and OF2 with execution times of 12 ns and 8 ns respectively.

The speedup (correct to two decimals places) achieved by EP over NP in executing 20 independent instructions with no hazards is ________________.

1.50-1.51 is the correct answer.

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CS and IT GATE 2017 Set-1 Questions with Answer