# ISRO CS 2014

 Question 1
Consider a 33 MHz CPU based system. What is the number of wait states required if it is interfaced with a 60 ns memory? Assume a maximum of 10 ns delay for additional circuitry like buffering and decoding.
 A 0 B 1 C 2 D 3
Computer Organization and Architecture    ISRO CS 2014    Pipelining and Addressing modes
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Question 1 Explanation:
A wait state is a delay experienced by a computer processor when accessing external memory or another device that is slow to respond. Total memory access time = 60 ns + 10 ns = 70 ns. Given, CPU frequency = 33 MHz So, 1 clock time = 1 / (33 MHz) = (1/33)*10-6 = 30.30 ns. Therefore, Total number of wait states = Total number of cycle needed = 70 ns / (30.30 ns) = 2.31 ≈ 3 cycles. So, option (D) is correct.
 Question 2
The number of states required by a Finite State Machine, to simulate the behavior of a computer with a memory capable of storing 'm' words, each of length 'n' bits is?
 A m x 2n B 2m+n C 2mn D m+n
Regular languages and finite automata    ISRO CS 2014
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Question 2 Explanation:
Given, 'm' words, each of length 'n' bits, so total number of bits = m*n A state of finite state automata can store 1 bit of data, and a state can have either 0 or 1. Therefore, total number of states required by a Finite State Machine = 2mn. So, option (C) is correct.
 Question 3
What is the output of the following C program?
```#include<stdio.h>
#define SQR(x) (x*x)
int main()
{
int a;
int b=4;
a=SQR(b+2);
printf("%dn",a);
return 0;
}
```
 A 14 B 36 C 18 D 20
C Macro & Preprocessor    ISRO CS 2014
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Question 3 Explanation:
#define SQR(x) (x*x) a = SQR(b+2); a = (b + 2*b + 2) = (4 + 2*4 + 2) = 14 So, option (A) is correct.
 Question 4
Consider the following pseudo code
```while (m < n)
if (x > y ) and (a < b) then
a=a+1
y=y-1
end if
m=m+1
end while ```
What is cyclomatic complexity of the above pseudo code?
 A 2 B 3 C 4 D 5
Software Engineering    ISRO CS 2014
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Question 4 Explanation:
Draw the Control Flow Graph (CFG) for given pseudo code: Now, cyclomatic complexity:
```= (number of edges) - (number of nodes) + 1 = 8-6+2 = 4
= Total number of regions = 4
= Total number of decision points + 1 = 3+1 = 4 ```
Note that decision points at a node = (total number of outgoing edges) - 1. So, option (C) is correct.
 Question 5
What is the number of steps required to derive the string ((() ()) ())
```S → SS
S → (S)
S → ε
```
 A 10 B 15 C 12 D 16
Context free languages and Push-down automata    ISRO CS 2014
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Question 5 Explanation:
To generate ((() ()) ()) , following steps are needed:
```1) S → (S)
2) S → (SS)
3) S → ((S)S)
4) S → ((SS)S)
5) S → (((S)S))S)
6) S → (((S)(S))S)
7) S → (((S)(S))(S))  [S → ε]
8) S → ((()(S))S)     [S → ε]
9) S → ((()())S)      [S → ε]
10) S → ((()()))
```
Option (A) is correct.
 Question 6
The process of modifying IP address information in IP packet headers while in transit across a traffic routing device is called
 A Port address translation (PAT) B Network address translation (NAT) C Address mapping D Port mapping
Network Layer    ISRO CS 2014
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Question 6 Explanation:
 Question 7
What does a pixel mask mean?
 A string containing only 1's B string containing only 0's C string containing two 0's D string containing 1's and 0’s
ISRO CS 2014    Computer Graphics
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Question 7 Explanation:
Pixel counts for the span length and interspan spacing can be specified in a pixel mask, which is a string containing the digits 1 and 0 to indicate which positions to plot along the line path. The mask 1111000, for instance, could be used to display a dashed line with a dash length of four pixels and an interdash spacing of three pixels. So, option (D) is correct.
 Question 8
In the standard IEEE 754 single precision floating point representation, there is 1 bit for sign, 23 bits for fraction and 8 bits for exponent. What is the precision in terms of the number of decimal digits?
 A 5 B 6 C 7 D 8
Number Representation    ISRO CS 2014
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Question 8 Explanation:
Precision can be understood as the maximum accuracy through which a floating point number can be represented. It is the smallest change that can be represented in floating point representation. The fractional part of a single precision normalized number has exactly 23 bits of resolution, (24 bits with the implied bit). In terms of decimal representation: let the number of digits in decimal digits be 'x' 2-23 = 10-x taking log log210-x = -23 -x log210 = -23 -3.322 x = -23 x = 6.92 So, correct answer is (C)
 Question 9
Let be the radius of the circle. What is the angle subtended by an arc of length at the center of the circle?
 A 1 degree B 1 radian C 90 degrees D π radians
General Aptitude    ISRO CS 2014
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Question 9 Explanation:
Radian describes the plane angle subtended by a circular arc as the length of the arc divided by the radius of the arc. One radian is the angle subtended at the center of a circle by an arc that is equal in length to the radius of the circle. Note that 1 radian = 57.2958 degree. So, option (B) is correct.
 Question 10
The number of logical CPUs in a computer having two physical quad-core chips with hyper threading enabled is
 A 1 B 2 C 8 D 16
Computer Organization and Architecture    ISRO CS 2014    Secondary memory and DMA
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Question 10 Explanation:
Every physical CPU corresponds to 2 logical CPU in hyperthreading and there are 2 quad core chips. Therefore, total number of physical CPUs = 2*4 = 8 Now, 8 physical CPU corresponds to 2*8 = 16 logical CPU. Note that a multi-core processor is a single piece of hardware ("one processor") that provides several cores than can work concurrently. So, option (D) is correct.
There are 80 questions to complete.

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