**AIM:**

**Study and Implementation of Looping Statements (for loop and while loop).**

**THEORY:**

Loops are MATLAB constructs
that permit us to execute a sequence of statements more than once. There are
two basic forms of loop constructs: while
loops and for loops. The major difference
between these two types of loops is in how the repetition is controlled. The code
in a while loop is repeated an indefinite number of times until some
user-specified condition is satisfied. By contrast, the code in a “for loop” is
repeated a specified number of times, and the number of repetitions is known
before the loops starts.

**1. For Loop:**

The for loop is a loop that executes a block of statements a
specified number of times.

**Syntax:**

For index =
expression

Statement;

Statement;

End

where index
is the loop variable (also known as the loop index) and expr is the loop
control expression, whose result is an array. The columns in the array produced
by expr are stored one at a time in the variable index, and then the loop body
is executed, so that the loop is executed once for each column in the array
produced by expr. The expression usually takes the form of a vector in shortcut
notation first:incr:last.

**2. While Loop:**

A while loop is a block of statements
that are repeated indefinitely as long as some condition is satisfied.

**Syntax:**

While
(Control Expression)

Statement;

End

**Fig: Flow Diagram of While Loop**

The
controlling expression produces a logical value. If the expression is true, the code block will be executed, and then
control will return to the while statement. If the expression is still true, the statements will be executed again.
This process will be repeated until the expression
becomes false. When control returns to the while statement and the
expression is false, the program will execute the first statement after the
end.

**PROCEDURE:**

**1. Program for finding factorial of given number using while loop:**

Using while
loop just implement factorial of a given number. First assign 0! Is 1 and 1! Is
also 1.

**2. Program for finding PSNR using for loop:**

The PSNR is
calculated by using following formula.

MAX

_{I}=Maximum value of pixel in Original image
m=No. of Row
in Original image

**n= No. of Column in Original image**

1. If Original Image is equal to Noisy Image then PSNR is 100%.

2. Find out difference between Original Image & Noisy
Image.

3.
Find
out Mean Square Error by using above formula.

4. Find out maximum value of Pixel in Original
Image.

5. Find out Peak Signal to Noise Ratio.

**1. Program for Finding Factorial using While loop:**

**Program:**

% Factorial finding

a=input('Enter value
for factorial = ');

fact=1;

while(a>1)

fact=fact*a;

a=a-1;

end

disp('Factorial of
given value is');fact

**Output:**

Enter
value for factorial = 6

Factorial
of given value is

fact
=720

**2. Program for PSNR using for loop**

**Program:**

% PSNR using foe loop

ori=input('Enter
Original Matrix = ');

noi=input('Enter Noisy
Matrix = ');

if (ori==noi)

PSNR=100;

else

[r c]=size(ori);

d = 0 ;

for i = 1:r-1

for j = 1:c-1

d = d + (ori(i,j) -
noi(i,j))^2 ;

end

end

MSE=d/(r*c);

MAX = max( abs(ori(:))
);

PSNR=
10*log10(MAX^2/MSE);

end

disp('PSNR is');PSNR

**Output:**

Enter
Original Matrix = [2 3 4;4 5 6;1 2 3]

Enter
Noisy Matrix = [6 7 8;4 5 6;2 3 4]

PSNR
is

PSNR
=10.0540

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