Test threads in C

test.c

#include <stdio.h>
#include <pthread.h>

void* calculate()
{
    int i = 0;
    int b = 0;
    for(i=0; i<100000000; i++){
        b = i+b;
    }
}


int main()
{
    int threads = 8;
    pthread_t sum[threads];
    int i = 0;
    
    for (i = 0; i<threads; i++)
    {
        printf("thread started\n");
        pthread_create(&sum[i], NULL, calculate, NULL);
    }
    for (i = 0; i<threads; i++)
    {
        pthread_join(sum[i], NULL);
        printf("thread end\n");
    }    
}
// gcc test.c -o program -lpthread; ./program