Solution of c languages:E.Balagurusamy

                                     Chapter-06           

               Decision making and looping                  

                          REVIEW QUESTIONS

6.1 State whether the following statements are true or false:

            (a) The do… while statement first executes the loop body and then evaluate the loop       control expression.

            Ans:  True.

            (b) In a preset loop, if the body is executed n terms,  the test expression is executed n+1 times.

            Ans:  True.

            (c) The number of times a control variable is updated always equals the number of loop iterations.

            Ans: True.

            (d) Both the preset loops include initialization within the statement.

            Ans: True.

(e) In a for loop expression, the starting value of the control variable must be less than its ending value.

            Ans: True.

(f) The initialization, test condition and increment parts may be missing in a for statement.

            Ans: False.

            (g) While loops can be used to replace for loops without any change in the body of the    loop.

Ans: False.

            (h) An exit control loop is executed a minimum of a one line.

            Ans: False.

(i) The use of continue statement considered as unstructured programming.

            Ans: True.

(j) The three loop expressions used in a for loop header must be separated by commas.

            Ans: True.

6.2: Fill in the blanks in the following statements.

            (a) In an exit controlled loop, if body is executed n times, test condition is evaluated   ­­­­­­­­­­­­­­­

            times.

            Ans: (n-1)

            (b) The            statements is use to skip a part of the statements in a loop.  

            Ans: continue.

            (c) A  for loop with the no test condition is known as         loop.

            Ans: infinite

            (d) The sentinel controlled loop is also; known as                    loop.

            Ans: indefinite repetition.

            (e)In a counter controlled loop, variable known as            is used to count the loop            operation.

            Ans: definite repetition.

6.8 explain the operation of each of the following for loops. 

             (a)for (n=1;n!=10;n+=2)

             sum=sum+n;

            Ans :The loop repeats 5 times.

            (b)for(n=5;n<=m;n-=1)

            sum+=n;

            Ans: The continue until n<=m where m initializes from 5 and decrements by 1.

            (c) for(n=1;n<=5)

            sum+=n;

            Ans: Since theren is no increment or decrement condition the loop repeats 5 times.

            (d) for(n=1;  ;n+=1)

            sum+=n;

            Ans: The loop repeats  infinity times.

(e)for(n=1;n<5;n++)

            n=n-1;

            Ans: The loop repeats  infinity times.

6.9: what would be the output of each of the following code segments?

            (a)count=5;

            while(count-- >0)

printf(“count”);

Output:

            5  4  3  2  1

            (b)count=5;

            while(-- count>0)

            Printf(“count”);

Output:

            4  3  2  1

            (c)  count=5;

            do  printrf(“count”);

            while(count>0)

Output:

            5  4  3  2  1

(d)for(m=10;m>7;m-=2)

            printf(“m”);

            output;

            10  8

6.11:Analyse each of the program segment that follow the determine how many times the body of each loop will be executed.

            (a)x=5;

 y=50;

while(x<=y)

{

              x=y/x;

…………………..

…………………..

            }

            Ans: Infinity times

(b) m=1;

            do

{

             ……………………

……………………….

m+=2;

}

while(m<10)

             Ans: 5 times.

(c) int i;

for(i=0;i<=5;i=i+2/3)

{

 …………………..

…………………….

}

Ans: Infinity times.

(d) int m=10;

Int n=7;

while(m%n>=0)

{

………………

m+=1;

n+=2;

…………….

}

Ans: 4 times.

6.12:   Find errors, if any, in each of the following looping segments. Assume that all the variables have been declared and assigned values.

(a)while(count!=10);

{

count=1;

sum+=x;

count+=1;

}

Error: while(count!=10);

Correct Ans: while(count!=10)

(b) name=0;

do

{

name+=1;

printf(“my name is Dinar\n”);

while(name=1);

Error: while (name=1);

Correct Ans: while(name==1);

(c) do;

total+=value;

scanf(“%f”,&value);

while(value!=999);

Error: do;

Correct Ans: do

(E) m=1;

n=0;

for(p=10;p>0;)

p-=1;

printf(“%f”,p);

Error: for(p=10;p>0;)

p-=1;

printf(“%f”,p);

Correct ans: for(p=10;p>0;)

{

p-=1;

printf(“%f”,p);

}

6.13:Write a for statement to pront each of the following sequence of integers:

(a) 1,2,4,8,16,32

Ans: for(i=1;i<=32;i=i*2)

 printf(“%d”,i);

(b) 1,3,9,27,81,243

Ans: for(i=1;i<=243;i=i*i)

printf(“%d”,i);

(c) -4,-2,0,4

for(i=-4;i<=4;i=i+2)

printf(“%d”,i);

(d) -10,-12,-14,-18,-26,-42

for(i=-10;i<=-42;i=i-2)

printf(“%d”,i);

6.14: Change the following for loops to while loops :

(a)for(m=1;m<10;m=m+1)

printf(“m”);

Ans: m=1;

while(m<10)

{

…………….

m++;

}

printf(“m”);

(b)for(;scanf(“%d”,&m)!=-1;)

printf(“m”);

Ans: 

while(scanf(“%d”,&m)!=-1)

printf(“m”);

6.16: What is the output of following code?

Int m=100,n=0;

while(n==0)

{

if(m<10)

break;

m=m-10;

}

Output: No output

6.17: What is output of the following code?

int m=0;

do

{

if(m>10)

             continue;

            m=m+10;

}

while(m<50);

 printf(“%d”,m);

Output: 50

6.18: What is the output of the following code?

int n=0,m=1;

do

{

             printf(“m”);

m++;

}

while(m<=n);

             Output: 1

6.19: What  is the output of the following code?

            int n=0,m;

            for(m=1;m<=n+1;m++)

printrf(“m”);

Output: 1

6.20: When do we use the following statement?

for(;  ;)

Ans : When we need an infinity loop the statement for(; ;) can be used.