Decision Making and Looping

Flow Control Statements
(Looping)

Iteration Statements
• Iteration statements is also known as Looping statement.
• A segment of the program that is executed repeatedly is called as a loop.
• Some portion of the program has to be specified several number of times or until a particular condition
is satisfied.
• Such repetitive operation is done through a loop structure.
• The Three methods by which you can repeat a part of a program are,
• while Loops
• do….while loops
• for Loop
Loops generally consist of two parts :
Control expressions: One or more control expressions which control the execution of the
loop,
Body : which is the statement or set of statements which is executed over and over
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Any looping statement , would include the following steps:
• Initialization of a condition variable
• Test the control statement.
• Executing the body of the loop depending on the condition.
• Updating the condition variable.
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While Loop
A while loop has one control expression, and executes as long as that
expression is true. The general syntax of a while loop is
A while loop is an entry controlled loop statement.
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initialize loop counter;
while (condition)
{
statement (s);
increment or decrement loop counter
}

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Start
Initialize
Test Condition
Body of Loop
Increment or Decrement
Stop
False
True

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Example:
// Print the I Values
#include <stdio.h>
void main()
{
int i;
i = 0;
while(i<=10)
{
printf(“The I Value is :%dn”, i );
++i;
}
}
// Summation of the series 1 + 2 + 3 + 4 +
…….
#include <stdio.h>
void main()
{
int i, sum;
i = 1;
sum = 0;
while(i<=10)
{
sum = sum + I;
printf(“The Sum Value is:%dn”,i);
++i;
}
}

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Example:
//Summation of the series 12 + 22 + 32 + …..
#include <stdio.h>
#include<math.h>
void main()
{
int i, sum;
i = 1;
sum = 0;
while(i<=10)
{
sum = sum + i*i; //or I ^2 or pow(i, 2)
++I;
}
}
//Summation of the series 11 + 22 + 33 + …..
#include <stdio.h>
#include<math.h>
void main()
{
int i, sum;
i = 1;
sum = 0;
while(i<=10)
{
sum = sum + pow(i,i)
++i;
}
}

#include<stdio.h>
void main()
{
int number=0, rem=0, sum=0;
printf(“Enter the value for number”);
scanf(“%d”, &n);
while(number > 0)
{
rem = number % 10;
sum = sum + rem;
number = number / 10;
}
printf(“the summation value of the given number %d is = %d”, number, sum);
}
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Program to print the summation of digits of any given number.

THE do-while LOOP
• The body of the loop may not be executed if the condition is not satisfied in while loop.
• Since the test is done at the end of the loop, the statements in the braces will always be executed at
least once.
• The statements in the braces are executed repeatedly as long as the expression in the parentheses is
true.
Make a note that do while ends in a ; (semicolon)
Note that Do… While Looping statement is Exit Controlled Looping statement 11/29/2020 9
initialize loop counter;
do
{
statement (s);
increment or decrement loop counter
}
while (condition);

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Start
Initialize
Test Condition
Body of Loop
Increment or Decrement
Stop
False
True

S. No. while loop do-while loop
1.
The while loop tests the condition
before each iteration.
The do – while loop tests the
condition after the first
iteration.
2.
If the condition fails initially the
loop is Skipped entirely even in
the first iteration.
Even if the condition fails initially
the loop is executed once.
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Difference Between While Loop and Do – While Loop

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Example:
#include <stdio.h>
void main()
{
int i;
i = 0;
do
{
printf(“The I Value is :%dn”, i);
++i;
}
while(i<=10);
}
#include <stdio.h>
void main()
{
int i;
i = 11;
do
{
printf(“The I Value is :%dn”, i);
++i;
}
while(i<=10);
}

#include <stdio.h>
void main()
{
int i, f1,f2,f3;
f1 = 0;
f2 = 1;
printf(“The Fibonacci Series is:n”)
printf(“%dn”,f1);
printf(“%dn”,f2);
do
{
f3 = f1 + f2;
printf(%dn”, f3);
f1 = f2;
f2 = f3;
++i;
}
while(i <= 10);
}
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Program to print the Fibonacci series for any given number Using Do….While Loop

for Loop
• The for loop is another repetitive control structure, and is used to execute set of instruction repeatedly
until the condition becomes false.
• To set up an initial condition and then modify some value to perform each succeeding loop as long as
some condition is true.
The syntax of a for loop is
The three expressions :
expr1 - sets up the initial condition,
expr2 - tests whether another trip through the loop should be taken,
expr3 - increments or updates things after each trip. 11/29/2020 14
for( expr1; expr2 ;expr3)
{
Body of the loop;
}

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Start
Initialize; test_condition; Increment / Decrement
Body of Loop
Stop

Example
#include<stdio.h>
void main()
{
for (int i = 1; i <= 10; i++)
printf("i is %dn", i);
}
There is no need of { } braces for single line statement and for
multiple line it is
essential else it will consider only next line of for statement.
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Given example will print the values from 1 to 10.

Example
#include<stdio.h>
#include<conio.h>
void main()
{
int mul, limit, c, i;
printf("Enter the Multiplication Number:n");
scanf("%d", &mul);
printf("Enter the Limits:n");
scanf("%d", &limit);
for(i=1;i<=limit;i++)
{
c = i * mul;
printf("%d * %d: %dn", i, mul, c);
}
}
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Given example of Multiplication Table

Additional Features of for Loop
Case 1:
The statement
p = 1;
for (n = 0; n < 17; ++ n)
can be rewritten as
for (p = 1, n = 0; n < 17;++n)
Case 2:
The second feature is that the test – condition may have any compound relation and
the testing need not be limited only to the loop control variable.
sum = 0;
for (i = 1; i < 20 && sum < 100; ++ i)
{
sum = sum + i;
printf(“%d %dn”, i, sum);
}
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Additional Features of for Loop Conti…
Case 3:
It also permissible to use expressions in the assignment statements of initialization
and increments sections.
For Example:
for (x = (m + n) / 2; x > 0; x = x / 2)
Case 4:
Another unique aspect of for loop is that one or more sections can be omitted, if
necessary.
For Example:
m = 5;
for ( ; m ! = 100 ;)
{
printf(“%dn”, m);
m = m + 5;
}
Both the initialization and increment sections are omitted in the for statement. The
initialization has been done before the for statement and the control variable is incremented
inside the loop. In such cases, the sections are left ‘blank’. However, the semicolons
separating the sections must remain. If the test – condition is not present, the for statement
sets up an ‘infinite’ loop. Such loops can be broken using break or goto statements in the
loop.
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Case 5:
We can set up time delay loops using the null statement as follows:
for ( j = 1000; j > 0; j = j – 1)
1. This is loop is executed 1000 times without producing any output; it
simply causes a
time delay.
2. Notice that the body of the loop contains only a semicolon, known as a
null statement.
Case 6:
for ( j = 1000; j > 0; j = j – 1)
This implies that the C compiler will not give an error message if we place
a semicolon by mistake at the end of a for statement. The semicolon will be
considered as a null statement and the program may produce some
nonsense.
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Additional Features of for Loop Conti…

Nesting of for Loop
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The One for statement within another for statement is called Nesting for Loop.
Syntax:
for (initialize; test_condi; incre. / decre.)
{
---------------
---------------
for (initialize; test_condi; incre. / decre.)
{
-----------
-----------
}
---------------
---------------
}
-----------------
-----------------
Outer
for LoopInner for
Loop

Example
// Print the I and J Value
#include<stdio.h>
#include<conio.h>
void main()
{
int I, j;
for (i = 1; I < = 10 ; I ++)
{
printf (“The I Value is %d n", i);
for (j = 1; j < = 10; j ++)
{
printf (“The J Value is %d n", j);
}
}
} 11/29/2020 22

Example
// Multiplication Table
#include<stdio.h>
#include<conio.h>
void main()
{
int sum = 1,a,b;
for (a=1;a<=5;a++)
{
printf ("the multiplication table for %dn",a);
for (b=1;b<=12;b++)
{
sum=a*b;
printf("%d*%d=", a, b);
printf("%dn", sum);
}
sum = 0;
}
}
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1. Loops perform a set of operations repeatedly until the control variable fails to satisfy the
test – condition.
2. The number of times a loop is repeated is decided in advance and the test condition is
written to achieve this.
3. Sometimes, when executing a loop it becomes desirable to skip a part of the loop or to
leave the loop as soon as a certain condition occurs.
4. Jumps out of a Loop is Classified into three types:
1. break;
2. continue;
3. goto;
JUMPS IN LOOPS

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The break Statement:
1. A break statement is used to terminate of to exit a for, switch, while or do – while statements
and the execution continues following the break statement.
2. The general form of the break statement is
3. The break statement does not have any embedded expression or arguments.
4. The break statement is usually used at the end of each case and before the start of the next
case statement.
5. The break statement causes the control to transfer out of the entire switch statement.
break;

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#include <stdio.h>
void main()
{
int i;
i = 1;
while (i < = 10)
{
printf (“The I Value is: %d n”, i);
if (i = = 6)
{
printf (“The I value is Reached 6, So break of the programsn”);
break;
}
++ I;
}

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#include<stdio.h>
void main ()
{
int num1,num2,choice;
printf (“Enter the Two Numbers:n”);
scanf(“%d%d”,&num1,&num2);
printf(“1 -> Additionn””);
printf(“2->Subtractionn”);
printf(“3->Multiplicationn”);
printf(“4->Divisionn”);
printf (“Enter your Choice:n”);
scanf (“%d”, &choice);
switch (choice)
{
case 1:
printf (“Sum is %d n”, num1+num2);
break;
case 2:
printf (“Diif. is %d n”, num1-num2);
break;
case 3:
printf (“Product is %d n”, num1*num2);
break;
case 4:
printf (“Division is %d n”, num1/num2);
break;
default:
printf (“Invalid Choice…..n”);
}
}

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The continue Statement:
1. The continue statement is used to transfer the control to the beginning of the loop, there by terminating
the current iteration of the loop and starting again from the next iteration of the same loop.
2. The continue statement can be used within a while or a do – while or a for loop.
3. The general form or the syntax of the continue statement is
4. The continue statement does not have any expressions or arguments.
5. Unlike break, the loop does not terminate when a continue statement is encountered, but it terminates
the current iteration of the loop by skipping the remaining part of the loop and resumes the control tot
the start of the loop for the next iteration.
continue;

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#include <stdio.h>
void main()
{
int i;
i = 1;
while (i < = 10)
{
printf (“The I Value is: %d n”, i);
if (i = = 6)
{
printf (“The I value is Reached 6, But Continue this Programsn”);
continue;
}
++ i;
}

S. No. break continue
1.
Used to terminate the loops
or to exit loop from a
switch.
Used to transfer the control to
the start of loop.
2.
The break statement when
executed causes
immediate termination of
loop containing it.
Continue statement when
executed causes Immediate
termination of the current
iteration of the loop.
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Differences Between Break and Continue Statement

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The goto Statement:
1. The goto statement is used to transfer the control in a loop or a function from one point to any other
portion in that program.
2. If misused the goto statement can make a program impossible to understand.
3. The general form or the syntax of goto statement is:
4. The goto statement is classified into two types:
1. Unconditional goto.
2. Conditional goto.
goto label;
Statement (s);
…………….
label:
statement (s);

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Unconditional Goto:
The Unconditional goto means the control transfer
from one block to another block without checking the test
condition.
Example:
#include <stdio.h>
void main()
{
Start:
printf(“Welcomen”);
goto Start;
}

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Conditional Goto:
The Conditional goto means the control transfer from one block to
another block with checking the test condition.
#include <stdio.h>
void main()
{
int a, b;
printf (“Enter the Two Value:n”);
scanf (“%d”, &a, &b);
if (a > b)
goto output_1;
else
goto output_2;
output_1:
printf (“A is Biggest Number”);
goto Stop;
output_2:
printf (“B is Biggest Number”);
goto Stop;
Stop:
}

Decision Making and Looping

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