# Prime Numbers between an interval | MATLAB Tutorial

## Printing all prime numbers between an interval using MATLAB

What is a Prime number?

• A Prime number is a natural number greater than 1 that has no positive divisors other than 1 and itself.
• It should not be divisible by any other number, else it is composite.
• 1 is neither prime nor composite.

Example:- Prime numbers between

1. 1 and 10 are
2, 3, 5, 7
2. 10 and 20 are
11, 13, 17, 19
3. 30 and 40 are
31, 37.
4. 100 and 200 are
101103107109113127131137139149,151157163167173179181, 191, 193197,199.

MATLAB CODE

```

a=input('Enter first no.');
b=input('Enter second no.');

if(a<0||b<0||a>b)
error('Error')
end
for j= 0:b-a
flag=0;
for i=2:(a+j)/2;
if (mod((a+j),i)==0)
flag=1;
end
end
if flag==0
fprintf('%d',a+j);
fprintf('\n');
end
end

```

Algorithm

• The user should enter two numbers which then becomes the two extreme points of an interval.
• Those two numbers are then stored in two variables.
• The number entered first is divided by every number from 2 to half of the number and then the remainder is taken.
• If the remainder results in 0 then the ‘flag’ is made to be one. This ‘flag’ is used to decide whether a certain number is prime or not.
• If the number makes the flag as one it is a composite number, whereas if it turns out that a number doesn’t turn or change the flag to one then it is not a composite number.
• Above process is repeated for every number between the interval entered by the user and the desired number is printed on the screen.

OUTPUT

1. Numbers between 10-100

2.Numbers Between 200-300

3. Error when a greater number is added first and a smaller number later

##### SAURAB S

I am currently pursuing my btech in Electronics and communication engineering from Amrita Vishwa Vidyapeetham. My areas of interest are signal processing, Communication systems, Control system.

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