**Definition of prime number:**

A
natural number greater than one has not any other divisors except 1 and itself.
In other word we can say which has only two divisors 1 and number itself. For
example: 5

Their
divisors are 1 and 5.

Note: 2
is only even prime number.

**Logic for prime number in c**

We will
take a loop and divide number from 2 to number/2. If the number is not divisible
by any of the numbers then we will print it as prime number.

**Example of prime numbers**: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199 etc.

Code 1:

1.

**C program to determine prime number**
2.

**Determining if a number is prime in c**
3.

**C program to find given number is prime or not**
#include<stdio.h>

int main(){

int num,i,count=0;

printf("Enter a number: ");

scanf("%d",&num);

for(i=2;i<=num/2;i++){

if(num%i==0){

count++;

break;

}

}

if(count==0 && num!= 1)

printf("%d is a prime
number",num);

else

printf("%d is not a prime
number",num);

return 0;

}

Sample output:

Enter a number: 5

5 is a prime number

Code 2:

1

**. C program for prime numbers between 1 to 100**
2.

**How to find prime numbers from 1 to 100 in c**
3.

**How to print prime numbers from 1 to 100 in c**
#include<stdio.h>

int main(){

int num,i,count;

for(num = 1;num<=100;num++){

count
= 0;

for(i=2;i<=num/2;i++){

if(num%i==0){

count++;

break;

}

}

if(count==0 && num!= 1)

printf("%d
",num);

}

return 0;

}

Output:

2 3 5 7 11 13 17 19 23 29 31 37
41 43 47 53 59 61 67 71 73 79 83 89 97

Code 3:

1.

**C program for prime numbers between 1 to n**
2.

**C program to find prime numbers up to n**
3.

**C program to list prime numbers**
4.

**Write a c program to generate n prime numbers**
5.

**C program to find n prime numbers**
#include<stdio.h>

int main(){

int num,i,count,n;

printf("Enter max range: ");

scanf("%d",&n);

for(num = 1;num<=n;num++){

count
= 0;

for(i=2;i<=num/2;i++){

if(num%i==0){

count++;

break;

}

}

if(count==0 && num!= 1)

printf("%d
",num);

}

return 0;

}

Sample output:

Enter max range: 50

2 3 5 7 11 13 17 19 23 29 31 37
41 43 47

Code 4:

1.

**C program to find prime numbers using while loop**
2.

**Wap to find prime numbers in c**
3.

**Write a c program to generate prime number**
4.

**How to get prime numbers in c**
#include<stdio.h>

int main(){

int
num,i,count,min,max;

printf("Enter
min range: ");

scanf("%d",&min);

printf("Enter max range: ");

scanf("%d",&max);

num
= min;

while(num<=max){

count
= 0;

i=2;

while(i<=num/2){

if(num%i==0){

count++;

break;

}

i++;

}

if(count==0 && num!= 1)

printf("%d
",num);

num++;

}

return 0;

}

Sample output:

Enter min range: 50

Enter max range: 100

53 59 61 67 71 73 79 83 89 97

Code 5:

1.

**How to find out prime numbers in c programming**
2.

**Display prime numbers in c**
3.

**C program to find prime numbers between two numbers**
4.

**C code to display prime numbers within a range**
#include<stdio.h>

int main(){

int
num,i,count,min,max;

printf("Enter min range: ");

scanf("%d",&min);

printf("Enter max range: ");

scanf("%d",&max);

for(num = min;num<=max;num++){

count
= 0;

for(i=2;i<=num/2;i++){

if(num%i==0){

count++;

break;

}

}

if(count==0 && num!= 1)

printf("%d
",num);

}

return 0;

}

Enter min range: 10

Enter max range: 50

11 13 17 19 23 29 31 37 41 43 47

Code 6:

1.

**Sum of prime numbers from 1 to 100 in c**
#include<stdio.h>

int main(){

int
num,i,count,sum=0;

for(num = 1;num<=100;num++){

count
= 0;

for(i=2;i<=num/2;i++){

if(num%i==0){

count++;

break;

}

}

if(count==0 && num!= 1)

sum
= sum + num;

}

printf("Sum of
prime numbers is: %d ",sum);

return 0;

}

Output:

Sum of prime numbers is: 1060

Code 7:

**1. C program to find sum of prime numbers**

#include<stdio.h>

int main(){

int
num,i,count,min,max,sum=0;

printf("Enter min range: ");

scanf("%d",&min);

printf("Enter max range: ");

scanf("%d",&max);

for(num = min;num<=max;num++){

count
= 0;

for(i=2;i<=num/2;i++){

if(num%i==0){

count++;

break;

}

}

if(count==0 && num!= 1)

sum
= sum + num;

}

printf("Sum of
prime numbers is: %d ",sum);

return 0;

}

Enter min range: 50

Enter max range: 100

1. Write a c program to check given number is perfect number or not.
Sum of prime numbers is: 732

10. Write a c program to add two numbers without using addition operator.

11. Write a c program to subtract two numbers without using subtraction operator.

15. Write a c program to solve quadratic equation.

18. Write a c program which passes structure to function.

28. Write a c program which takes password from user.

29. Write a scanf function in c which accept sentence from user.

30. Write a scanf function in c which accept paragraph from user.

## 57 comments:

nice ^_^ thanks

awesme practise for the beginners.........full fledge programs......:)))

hello sir,

suppose i want to search prime number between 1 to 200 and want to find largest prime number between result, how i can achieve this result?

example

min value=1

max valu=10

prime numbers between 1 to 10=2,5,7

large prime=7

please tell me the use of cont variable in this program and if possible then please explain the first program.

Excellent website for beginners

no need to divide the num by 2 just take sqrt of num and increase only check odd values (except 2) much efficient program Sir....

use this method to easily to understand

#include

#include

void main()

{

int i,j,a,n;

printf("enter the number");

scanf("%d",&a);

for(i=2;i<=n;i++)

{

}

if(a%i==0)

{

printf("the number is not prime");

}

else

{

printf("the number is prime");

}

getch();

}

realy helpfl......

Superb.....Thanx a lot.

what about 2?? for that the above logic will not work.. because 2%2=0, so it will not show as a prime number...

Q 4) Write a C++ program to print all prime numbers between two limits by using do while loop.

Q 5) Write a C++ program to search an element by using binary search.

Q 6) Write a C++ program to interchange two numbers by using function.

Thanks its realy helps

What is the value of n?

hello sir.

how can i print prime number by using if else condition. with out using any loop or other condition.

only in if else condition.......

can anyone please show the dry run of the second program please??

How to use strcmp() in c-language , please send a one example

Program to print prime number from 1 to n.

One solution may be like this :

# include

main()

{

int n, i, j, isPrime = 0;

scanf("%d\n",&n );

for(i = 2; i <= n; i++)

{

isPrime = 1;

for(j = 2; j <= i/2; j++)

{

if(i % j == 0)

{

isPrime = 0;

break;

}

}

if(isPrime)

printf("%d ",i);

}

}

#include

#include

int main(){

char str1[30],str2[30];

printf("Enter first string: ");

gets(str1);

printf("Enter second string: ");

gets(str2);

if(strcmp(str1,str2)==0)

printf("Both strings are equal");

else

printf("Strings are unequal");

return 0;

}

You can further more reduce the number of iterations.

As, for a number to be prime or not, it is not necessary to check upto 'number/2'.

Check only upto sqrt(number).

e.g.

TO check 23, check '23 % i == 0' only upto 'i <= sqrt(number)' i.e. {i <= 4}.

This will always work.

#include

#include

int main()

{

int i,j,n=100 ;

for(i=2;i<=n;i++)

{

for(j=2;j<i;j++)

{

if(i%j==0)

break;

}

if(i==j)

printf("\n%d",i);

}

system("PAUSE");

}

In this program why 4 is not printed?when 14 and j=4 then it should be print 4 as prime number(program works correctly :)).i dont understand nested loops.Can anybody please explain me the working of this program for say,n=10.i reach at 3 but 4 makes me in trouble.

In a global Mathematics contest, the contestants are told to invent some special numbers which can be built by adding the squares of its digits. Doing this perpetually, the numbers will end up to 1 or 4.

If a positive integer ends with 1, then it is called the Number of Game.

An example from above is:

13 = 1^2 + 3^2 = 1+9 = 10 (Step:1)

10 = 1^2 + 0^2 = 1+0 = 1 (Step:2), iteration ends in Step 2 since number ends with 1

Then in next round, the contestants are asked to combine their newly invented number, i.e. Number of Game with prime number.

Now, being a smart programmer, write a program to help the contestants to find out the Nth combined number within any given range, where N can be any integer.

Input Format:

Input consists of 3 integers X, Y, N, one on each line. X and Y are upper and lower limits of the range. The range is inclusive of both X and Y. Find Nth number in range [X,Y].

Line 1

X,where X is the upper limit of the range

Line 2

Y,where Y is the lower limit of the range

Line 3

N,where Nth element of the series is required

Constraints:

X <= Y

X > 0

N > 0

Output Format:

Output will show the Nth element of the combined series lying in the range between X and Y.

Line 1

For Valid Input,print

U,where U is the Nth element of the combined number series lying in the range between X and Y.

Or

No number is present at this index

For Invalid Input,print

Invalid Input

Sample Input and Output

SNo. Input Output

1 1,30,3 19

2 12,33,5 No number is present at this index

3 -5,@,4 Invalid Input

please answer how to solve this?

wap to find out the sum of all numbers between 1 to 100 which are divisible by 7 can plz any i can solve this?

if n=1

1

1

if n=2

1

2*2

2*2

1

like this for n=1 to 100

Exlnt

can anyone please say how count works in the first program??

#include

#include

#include

int main()

{

int num,i,count=0;

clrscr();

printf("Enter a number:\n");

scanf("%d",&num);

for(i=2;i<=sqrt(num);i++)

{

if(num%i==0)

{

count++;

break;

}

}

if(count>0)

printf("Not a prime");

else

printf("%d is a prime number",num);

getch();

return 0;

}

can you please explain working

Write a program that checks if a given number is prime but does not belong to the fibonaci series. The program should return 1 if the numer is prime and does not belong to the fibonaic series or 0 otherwise

#include

#include

void main (void)

{

int score1,score2,score3,average,rating1,rating2,call=0,reject=0,offer=0,choice=1;

char name;

while(choice==1)

{

printf("Enter name of Candidate");

scanf("%c",&name);

printf("\nscore of test1:");

scanf("%d",&score1);

printf("\nscore of test2:");

scanf("%d",&score2);

printf("\nscore of test3:");

scanf("%d",&score3);

printf("Enter Rating 1 of candidate :");

printf("and enter Rating 2 of candidate :");

scanf("%d%d",&rating1,&rating2);

average=((score1+score2+score3)/3);

if(score1>75 && score2>75 && score3>75 && average>80)

{

printf("the candidate selected for interviw");

call++;

}

else

{

printf("rejection letter is sent");

reject++;

printf("press 1 if you want to continue Else press any number\n");

scanf("%d",&choice);

continue;

}

printf("Enter round1 marks");

scanf("%d",&rating1);

printf("Enter round2 marks");

scanf("%d",&rating2);

if (rating1>5 && rating2>7)

{

printf("Offer letter has been sent\n");

offer++;

}

else

{

printf("rejection letter has been sent\n");

reject++;

continue;

}

printf("\nPress 1 if you want to continue else press any other number\n");

scanf("%d",&choice);

printf("the number of candidates whom offer letter has been sent:%d\n",offer);

printf("the number of candidates called for interview:%d\n",call);

printf("the number of candidates whom rejection letter has been sent:%d\n",reject);

getch();

}

program o genrate sequnce like

1111

1112

1121

1211

1213

....

HI can anyone tell me how to reverse a string. also wap to reverse a string in C?

In for loop when 2/2 gives the answer 1 it will false the for loop condition [for(i=2;i<num/2;i++)] so the compiler will check the first if condition which is satisfied in this case and as a result it will show 2 a prime number.

hey...

sir plz tell me how to make account to chat in your chat box i wana ask questions...

#include

#include

int main()

{

for(int i=1;i<=100;i++)

{

if(i%7==0)

cout<<i<<endl;

}

getch();

}

Q. how to find out given number is prime number or not?

A.

Note :

1. The number must divisible itself or divisible by 1.

2. 0 and 1 is not prime number

3. So less than 2 is invalid number to find out prime number.

4. Prime number starts with 2 ,3 ……………………..

Prime number Algorithm:

1. Check given number is less than 2 (invalid number to find prime number)

2. Check given number is less than or equal to three (if given number is 2 or 3 it is prime number)

3. Initialize array with 2,3,5,7 array size is 4.

4. Check given number is divisible by any one number from array values.

5. If it is divisible than it is not a prime number.

6. If not divisible than it is prime number.

main()

{

int arr[4]={2,3,5,7}

int given_numbr=49;

int i=0;

if(given_number <2){

printf(“Invalid number - pls choose must be number >=2 \n\n”);

exit(0);

}

If (given_number <=3){

printf(“given number is prime number \n”);

exit(0);

}

While (i<=3){

If( given_number %(arr[i]) == 0){

Printf(“Number is prime =%d \n\n”,given_number);

i++;

Break;

}

i++;

}

If(i==4){

Printf(“%d - > not prime number \n\n”,given_number);

}

}

Mahesh vk

include

include

main()

{

int n,

frintf("enter n value");

scanf("%d",&n);

{

if(n==0,n/2)

}

printf("primary number")

{

else

printf(" odd number")

}

getch();

}

1. Write a program to find the largest sequence of numbers in an array which sums to any given number.

Example:

Consider an array: [1,2,3,5,6,7]

Given a number say 8.

Possible sequences: 3+5=8, 1+2+5=8, 2+6=8, 1+7=8, etc.

Output: (1,2,5)

Write efficient code to figure out the duplicates in an array of 1 to 100?

Write a program to achieve the following:

I/P: a-1-b-2-c-3(Linked list)

O/P should be: a-b-c-1-3-2

Logic should reverse every alternate element and append it to end of list.

I am very thankful to this program

#include

void main()

{

int num;

printf("enter the value");

scanf("%d",&num);

if(num==2||num==3)

{

printf("%d is a prime number ",num);

}

else if(num%2==0||num%3==0)

{

printf("%d is not a prime number ",num);

}

else

{

printf("%d is a prime number ",num);

}

}

char str[n];

cin >> str;

for( int i=0, j=n-1; i<j; i++, j-- )

{

temp = str[i];

str[i] = str[j];

str[j] = temp;

}

cout << str;

I don't understand why every published code checks for prime from 2 to n/2 although it can be solved by checking divisibility of n by numbers in range [2, sqrt(n)].

#include

int main()

{

int num,i,count=0;

printf("Enter a number: ");

scanf("%d",&num);

for(i=2;i<=sqrt(num);i++)

{

if(num%i==0)

{

count++;

break;

}

}

if(count==0 && num!= 1)

printf("%d is a prime number",num);

else

printf("%d is not a prime number",num);

return 0;

}

awesome

helpful

34,18,10,6,4...

can anyone help with a program to generate dis sequence?

program that checks if a given number is prime but does not belong to the Fibonacci series

the optimized version of above program in which we only test with numbers between 2 to sqrt(N). Testing with numbers till N/2 is not required.

for(i = 2; i <= (int)sqrt(num); ++i) {

if(num%i==0) {

isPrime=1;

break;

}

}

C program to check prime number

C program examples

Prime number program in c

Thanks for sharing useful code

hey

why is the for loop till n/2 in the prime number question?

I want tht code of prime no if i enter a range like 10 or 20 it prints 2,3,5,7 & 11,13,17,19 as output

I want the flowchart for identifying prime number in c。。。。。。。please help

Write a ‘C’ function to generate the following figure for n = 7.

1

1 3

1 3 5

1 3 5 7

1 3 5

1 3

1

The value of n is passed to the function as an argument. Print the triangle only if n is odd otherwise print an error message.

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