Nested Loops in C unit2.docx

Conditional execution and selection
Nested Loops in C
C supports nesting of loops in C. Nesting of loops is the feature in C
that allows the looping of statements inside another loop. Let's
observe an example of nesting loops in C.
Any number of loops can be defined inside another loop, i.e., there is
no restriction for defining any number of loops. The nesting level can
be defined at n times. You can define any type of loop inside another
loop; for example, you can define 'while' loop inside a 'for' loop.
Syntax of Nested loop
1. Outer_loop
2. {
3. Inner_loop
4. {
5. // inner loop statements.
6. }
7. // outer loop statements.
8. }
Outer_loop and Inner_loop are the valid loops that can be a 'for'
loop, 'while' loop or 'do-while' loop.
Nested for loop
The nested for loop means any type of loop which is defined inside the
'for' loop.
for (initialization; condition; update)
{
for(initialization; condition; update)

{
// inner loop statements.
}
// outer loop statements.
}
Example of nested for loop
#include <stdio.h>
int main()
{
int n;// variable declaration
printf("Enter the value of n :");
// Displaying the n tables.
for(int i=1;i<=n;i++) // outer loop
{
for(int j=1;j<=10;j++) // inner loop
{
printf("%dt",(i*j)); // printing the value.
}
printf("n");
}
Explanation of the above code
o First, the 'i' variable is initialized to 1 and then program control
passes to the i<=n.
o The program control checks whether the condition 'i<=n' is true
or not.

o If the condition is true, then the program control passes to the
inner loop.
o The inner loop will get executed until the condition is true.
o After the execution of the inner loop, the control moves back to
the update of the outer loop, i.e., i++.
o After incrementing the value of the loop counter, the condition is
checked again, i.e., i<=n.
o If the condition is true, then the inner loop will be executed
again.
o This process will continue until the condition of the outer loop is
true.
Output:
Nested while loop
The nested while loop means any type of loop which is defined inside
the 'while' loop.
while(condition)
{
while(condition)

{
}
}
Example of nested while loop
#include <stdio.h>
int main()
{
int rows; // variable declaration
int columns; // variable declaration
int k=1; // variable initialization
printf("Enter the number of rows :"); // input the number of rows.
scanf("%d",&rows);
printf("nEnter the number of columns :"); // input the number of columns
scanf("%d",&columns);
int a[rows][columns]; //2d array declaration
int i=1;
while(i<=rows) // outer loop
{
int j=1;
while(j<=columns) // inner loop
{
printf("%dt",k); // printing the value of k.
k++; // increment counter
j++;

}
i++;
printf("n");
}
}
Explanation of the above code.
o We have created the 2d array, i.e., int a[rows][columns].
o The program initializes the 'i' variable by 1.
o Now, control moves to the while loop, and this loop checks
whether the condition is true, then the program control moves to
the inner loop.
o After the execution of the inner loop, the control moves to the
update of the outer loop, i.e., i++.
o After incrementing the value of 'i', the condition (i<=rows) is
checked.
o If the condition is true, the control then again moves to the inner
loop.
o This process continues until the condition of the outer loop is
true.

Nested do..while loop
The nested do..while loop means any type of loop which is defined
inside the 'do..while' loop.
do
{
do
{
}
while(condition);
}
while(condition);

Example of nested do..while loop.
#include <stdio.h>
int main()
{
/*printing the pattern
********
********
********
******** */
int i=1;
do // outer loop
{
int j=1;
do // inner loop
{
printf("*");
j++;
}
while(j<=8);
printf("n");
i++;
}
while(i<=4);
}
Output:

Explanation of the above code.
o First, we initialize the outer loop counter variable, i.e., 'i' by 1.
o As we know that the do..while loop executes once without
checking the condition, so the inner loop is executed without
checking the condition in the outer loop.
o After the execution of the inner loop, the control moves to the
update of the i++.
o When the loop counter value is incremented, the condition is
checked. If the condition in the outer loop is true, then the inner
loop is executed.
o This process will continue until the condition in the outer loop is
true.
Array
An array is defined as the collection of similar type of data items stored at contiguous
memory locations. Arrays are the derived data type in C programming language which
can store the primitive type of data such as int, char, double, float, etc.
It also has the capability to store the collection of derived data types, such as pointers,
structure, etc. The array is the simplest data structure where each data element can be
randomly accessed by using its index number.

C array is beneficial if you have to store similar elements.
For example, if we want to store the marks of a student in 6 subjects, then we don't
need to define different variables for the marks in the different subject.
Instead of that, we can define an array which can store the marks in each subject at
the contiguous memory locations.
By using the array, we can access the elements easily. Only a few lines of code are
required to access the elements of the array.
Properties of Array
The array contains the following properties.
o Each element of an array is of same data type and carries the same size, i.e., int
= 4 bytes.
o Elements of the array are stored at contiguous memory locations where the first
element is stored at the smallest memory location.
o Elements of the array can be randomly accessed since we can calculate the
address of each element of the array with the given base address and the size of
the data element.
Advantage of C Array
1) Code Optimization: Less code to the access the data.
2) Ease of traversing: By using the for loop, we can retrieve the elements of an array
easily.
3) Ease of sorting: To sort the elements of the array, we need a few lines of code
only.
4) Random Access: We can access any element randomly using the array.
Disadvantage of C Array
1) Fixed Size: Whatever size, we define at the time of declaration of the array, we
can't exceed the limit. So, it doesn't grow the size dynamically like LinkedList which we
will learn later.

Declaration of C Array a[10]
We can declare an array in the c language in the following way.
1. data_type array_name[array_size];
Now, let us see the example to declare the array.
1. int marks[5];
Here, int is the data_type, marks are the array_name, and 5 is the array_size.
Initialization of C Array
The simplest way to initialize an array is by using the index of each element. We can
initialize each element of the array by using the index. Consider the following example.
1. marks[0]=80;//initialization of array
2. marks[1]=60;
3. marks[2]=70;
4. marks[3]=85;
5. marks[4]=75;
C array example
#include<stdio.h>
int main(){
int i=0;
int marks[5];//declaration of array
marks[0]=80;//initialization of array
marks[1]=60;
marks[2]=70;
marks[3]=85;

marks[4]=75;
//traversal of array
for(i=0;i<5;i++){
printf("%d n",marks[i]);
}//end of for loop
return 0;
}

Nested Loops in C unit2.docx

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