C Program to Check Whether given Number is Prime or Not | detect prime number or not in c Language
Program Description :
Write a Program to check whether a number is a prime number or not in C Language. The program should accept one Integer from the user and checks if it is prime or not.
What is Prime Number :
- A Prime Number can be divided evenly only by 1, or itself.
- A Prime Number must be a whole number greater than 1.
Example:
- 3 can only be divided evenly by 1 or 3, so it is a prime number.
- But 6 can be divided evenly by 1, 2, 3 and 6 so it is NOT a prime number.
Note : There are other efficient ways to write this program. we will discuss them in next posts.
Program to check number is Prime number or not in C Language :
We will use one flag variable and set that flag to 1 if the given number is evenly dividable by any number (except 1 and the given number). That’s why my for loop is started with 2 and ended at n/2
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#include<stdio.h>
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void main()
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{
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int FLAG,i,num;
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// first set the flag to 0
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FLAG = 0;
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printf(“Enter any positive Number : “);
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scanf(“%d”,&num);
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for(i=2;i<num/2 ; i++)
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{
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if(num%i == 0)
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{
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FLAG=1;
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break;
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}
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}
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// check if FLAG is 0 or 1
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// if FLAG is 0 then Number is Prime.
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// otherwise Number is not Prime.
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if(FLAG == 0)
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printf(“%d is Prime Number \n“,num);
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else
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printf(“%d is not a prime Number \n“,num);
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}
OUTPUT :
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| C Program to check given Number is Prime or not |
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