Question

a) Hand-trace the following program and determine and write down what is the output of the code.

               b) Run the code and compare the program output to your hand-traced result obtained from part (a).

#include <iostream>

#include <iomanip>

using namespace std;

void f();

int x = 5;

int main()

{

        cout << "x = " << x << endl;

        int x = 6;

        cout << "x = " << x << endl;

        {

               int x = 7;

               cout << "x = " << x << endl;

        }

        cout << "x = " << x << endl;

        f();

        return 0;

}

void f()

{

        cout << "x = " << x << endl;

       

        int x = 8;

        cout << "x = " << x << endl;

}

About arrays, you need to know the following in order to complete the programs:

·        How to declare 1D and 2D arrays

·        How to declare and initialize 1D and 2D arrays at the same time

·        How to load array elements with values entered by user

·        How to perform operations on array elements such as moving elements around (swapping)

·        How to perform computations with arrays such as summing up elements

·        How to perform search and sort with arrays – two of the many important applications of arrays

·        How to pass an array to a function

·        Arrays, pointers, and pointer arithmetic

Answer 1

Variable x is declared and initialised to 5 at line number 6 is a global variable.

Scope of global variable is through out the file.

Hence cout on x variable on line number 10 which is the first statement of main function refers to global variable X.

Hence output of first cout on x is 5.

Next local variable x is declared at line number 12 and initialised to 6.

The next cout on x on line number 13 gives the output as 6,

because now x refers to local variable declared at line 12.

At line 15, variable x is again declared and initialised to 7 but with a scope that is within angular braces'{' from line number 14 to 17.

Cout on variable x at line 16, whose scope is between line numbers 14 to 17. It is for the variable x that is declared at line 15.

Hence cout on x at line number 16 gives output  as 7.

Next cout on variable x on line number 18 refers to the variable x that is declared at line 12.

Hence cout on x gives output as 6.

At line 19 function f is called. Inside function f, first cout on variable X, refers to global variable.

Hence gives output is 5.

In next line variable X is again declared and initialised to 8 as local variable.

Next cout inside this function on variable X gives output as 8, as it refers to this function(own) local variable.

Hand traced and output of the program are same.

A.Declaring 1D and 2D arrays:

int a[10], b[10][5];

a[10] refers to 1D, where 10 denotes the number of elements available in the array a.

b[10][5] refers to 2D, where 10 denotes the number of rows and 5 denotes number of columns in array b.

B.Declare and initialise at same time

1D

int a[]={10,20,30};

2D

int b[]2]={10,20,30,40};

C.Load elements in array with values entered by user:

Using for loop it can be loaded

for(int i =0;i <10;i ++)

cin>>a[i];

D.For summing same for loop can be used

Sum=0;

for(int i =0;i <10;i ++)

sum+=a[i];