# Loops (For and While) and Control Statements in Octave

• Last Updated : 18 Aug, 2022

Control statements are expressions used to control the execution and flow of the program based on the conditions provided in the statements. These structures are used to make a decision after assessing the variable. In this article, we’ll discuss control statements like the if statement, for and while loops with examples.

## if condition

This control structure checks the expression provided in parenthesis is true or not. If true, the execution of the statements continues. Syntax :

```if (condition)
statements
...
...
end
(endif can also be used)```

Example :

## MATLAB

 `% initializing variables variable1 and variable2``variable1 = 20;``variable2 = 20;`` ` `% check the if condition``if` `variable1 == variable2,`` ` `% if the condition is true this statement will execute``disp(``'The variables are Equal'``);` `% end the if statement``endif;`

Output:

`The variables are Equal`

## if-else condition

It is similar to if condition but when the test expression in if condition fails, then statements in else condition are executed. Syntax :

```if (condition)
statements
...
...
else
statements
...
...
end
(endif can also be used)```

Example :

## MATLAB

 `% initializing variables variable1 and variable2``variable1 = 20;``variable2 = 40;` `% check the if condition``if` `variable1 == variable2,` `% if the condition is true this statement will execute``disp(``'The variables are Equal'``);` `% if the condition is false else statement will execute``else``disp(``'The variables are Not Equal'``);`` ` `%end the if-else statement``end``;`

Output:

`The variables are Not Equal`

## if-elseif condition

When the first if condition fails, we can use elseif to supply another if condition. Syntax :

```if (condition)
statements
...
...
elseif (condition)
statements
...
...
else
statements
...
...
end
(endif can also be used)```

Example :

## MATLAB

 `% initializing the variable var``var = 50;` `% check the if condition``if` `var < 50,``disp(``'The variable is less than 50'``);` `% check the elseif condition``elseif` `var > 50,``disp(``'The variable is greater than 50'``);` `% if both the above condition is false else``% statement will execute``else``disp(``'The variable is 50'``);` `% end the if..elseif.. statements``end``;`

Output:

`The variable is 50`

## for loop

It is a type of loop or sequence of statements executed repeatedly until exit condition is reached. Syntax :

```for var = expression
body
end
(endfor can also be used)```

Example 1 : Printing numbers from 1 to 5 :

## MATLAB

 `% the value of i will move from 1 to 5``% with an increment of 1``for` `i = 1:5,` `% displays value of i``disp(i);` `% end the for loop``end``;`

Output :

``` 1
2
3
4
5```

Example 2 : for loop with vectors :

## MATLAB

 `% making a column vector from 1 to 10``v = [1; 2; 3; 4; 5; 6; 7; 8; 9; 10];` `% the value of i will move from 1 to 10``% with an increment of 1``for` `i = 1:10,`` ` `% modifying the value of ith element``% in the column vector as v(i) * 10``v(i) = v(i) * 10;`` ` `% end the for loop``end``;`` ` `% displays the v vector with modified values``disp(v)`

Output :

```    10
20
30
40
50
60
70
80
90
100```

Example 4 : Program to print the Fibonacci series up to 10 elements using for loop :

## MATLAB

 `% create a row vector of 10 elements all as '1'``fibonacci = ones(1, 10);` `% the value of i will move from 3 to 10 over the``% increment of 1``for` `i = 3:10` `% the ith term of fibonacci will computed``% as the sum of its previous 2 terms``    ``fibonacci(i) = fibonacci(i - 1) + fibonacci(i - 2);` `% end the for loop``endfor` `% print the fibonacci series``disp(fibonacci)`

Output :

`    1    1    2    3    5    8   13   21   34   55`

## while loop

The while loop is another kind of loop iterated until a condition is satisfied. The testing expression is checked first before executing the body of the loop. Syntax :

```while (condition)
body
end
(endwhile can also be used)```

Example : Display numbers from 1 to 10 :

## MATLAB

 `% initializing the variable i with 1``i = 1;` `% while condition``while` `i <= 10` `% displaying the value of i``disp(i);` `% make an increment of 1 in the value of i``i = i + 1;` `% end the while loop``endwhile`

Output :

``` 1
2
3
4
5
6
7
8
9
10```

## break statement

It is used to exit from a loop. Example 1 : We will be making a row vector and will only modify the first 6 values using the break statement.

## MATLAB

 `% making a row vector of 1x10, starting from 1``% and the next value is +10 of it's previous value``v = [1:10:100];` `% the value of i will move from 1 to 10``% with an increment of 1``for` `i = 1:10,` `% making the ith element in vector to 0``v(i) = 0;` `% if the condition is true the break statement``% will execute and the loop will terminate``if` `i == 6,``break``;` `% end the if condition``end``;` `% end the for loop``end``;` `% displays the modified vector v``disp(v)`

Output :

`    0    0    0    0    0    0   61   71   81   91`

Example 2 : break statement with while loop :

## MATLAB

 `% initializing the variable i with 1``i = 1;` `% the while condition is always true``while` `true` `% display the value of i``disp(i);` `% display the below content``disp(" is less than 5");` `% make an increment of 1 in value of i``i = i + 1;` `% if the if condition is true loop will break``if` `i == 5,``break``;` `% end the if statement``end``;` `% end the while``end``;`

Output :

``` 1
is less than 5
2
is less than 5
3
is less than 5
4
is less than 5```

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