# 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.

0 | |

1 | |

2 | |

3 |

**Computer Organization and Architecture**

**ISRO CS 2014**

**Pipelining and Addressing modes**

**Discuss it**

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?

m x 2 ^{n} | |

2 ^{m+n} | |

2 ^{mn} | |

m+n |

**Regular languages and finite automata**

**ISRO CS 2014**

**Discuss it**

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 = 2

^{mn}. 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; }

14 | |

36 | |

18 | |

20 |

**C Macro & Preprocessor**

**ISRO CS 2014**

**Discuss it**

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 whileWhat is cyclomatic complexity of the above pseudo code?

2 | |

3 | |

4 | |

5 |

**Software Engineering**

**ISRO CS 2014**

**Discuss it**

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 = 4Note 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

10 | |

15 | |

12 | |

16 |

**Context free languages and Push-down automata**

**ISRO CS 2014**

**Discuss it**

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

Port address translation (PAT) | |

Network address translation (NAT) | |

Address mapping | |

Port mapping |

**Network Layer**

**ISRO CS 2014**

**Discuss it**

Question 6 Explanation:

**Network address translation (NAT)**is a method of remapping one IP address space into another by modifying network address information in the IP header of packets while they are in transit across a traffic routing device.

**Port Address Translation (PAT)**is an extension to network address translation (NAT) that permits multiple devices on a local area network (LAN) to be mapped to a single public IP address. The goal of PAT is to conserve IP addresses.

**Address mapping**(also know as pin mapping or geocoding) is the process of assigning map coordinate locations to addresses in a database. The output of address mapping is a point layer attributed with all of the data from the input database.

**Port mapping**or port forwarding is an application of network address translation (NAT) which redirects a communication request from one address and port number combination to another while the packets are traversing a network gateway, such as a router or firewall. So, option (B) is correct.

Question 7 |

What does a pixel mask mean?

string containing only 1's | |

string containing only 0's | |

string containing two 0's | |

string containing 1's and 0’s |

**ISRO CS 2014**

**Computer Graphics**

**Discuss it**

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?

5 | |

6 | |

7 | |

8 |

**Number Representation**

**ISRO CS 2014**

**Discuss it**

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 log_{2}10^{-x}= -23 -x log_{2}10 = -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?

1 degree | |

1 radian | |

90 degrees | |

π radians |

**General Aptitude**

**ISRO CS 2014**

**Discuss it**

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

1 | |

2 | |

8 | |

16 |

**Computer Organization and Architecture**

**ISRO CS 2014**

**Secondary memory and DMA**

**Discuss it**

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.