C Exercises: Find the sum of all the primes below ten thousand
C Programming Practice: Exercise-26 with Solution
A prime number is a natural number greater than 1 that cannot be formed by multiplying two smaller natural numbers. A natural number greater than 1 that is not prime is called a composite number. For example, 5 is prime because the only ways of writing it as a product, 1 × 5 or 5 × 1, involve 5 itself. However, 6 is composite because it is the product of two numbers (2 × 3) that are both smaller than 6.
The sum of the primes below 10 is 2 + 3 + 5 + 7 = 17.
Write a C programming to find the sum of all the primes below ten thousand.
C Code:
#include <stdio.h>
#include <stdlib.h>
int main(void)
{
char *temp;
unsigned i, j;
size_t num = 10000;
unsigned long long sum = 0ULL;
temp = calloc(num, sizeof *temp);
for (i = 2; i < num; i++) {
if (!temp[i]) {
sum += i;
for (j = i*2; j < num; j += i) {
temp[j] = 1;
}
}
}
free(temp);
printf("%llu\n", sum);
return 0;
}
Sample Output:
5736396
Flowchart:

C Programming Code Editor:
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C Programming: Tips of the Day
Maximum value of int:
In C:
#include <limits.h> then use int imin = INT_MIN; // minimum value int imax = INT_MAX;
or
#include <float.h> float fmin = FLT_MIN; // minimum positive value double dmin = DBL_MIN; // minimum positive value float fmax = FLT_MAX; double dmax = DBL_MAX;
Ref : https://bit.ly/3fi8yk9
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