factorial value & no of digits find & test for prime no & test for coprime no & prime no print till 100

factorial value of N no


#include<stdio.h>
int main()
{
    int a,i,b=1;
    printf("Enter no");
    scanf("%d",&a);
    for(i=a;i>=1;i--)
    b=b*i;
    printf("factorial of %d is %d",a,b);
    return 0;

}


no of digits finding


#include<stdio.h>
int main()
{
    int a,x=0;
    printf("Enter no");
    scanf("%d",&a);
    while(a)
    {
     a=a/10;
     x++;
    } 
    printf("%d",x);
    return 0;
}


test for prime no


#include<stdio.h>
int main ()
{
    int a,b,c=0;
    printf("Enter no");
    scanf("%d",&a);
    for(b=1;b<=a;b++)
    {
        if(a%b==0)
        c++;
    }
    if (c==2)
    printf("Prime no");
    else
    printf("Not a prime no");
    return 0;
}


test for two no whether they both prime or not



#include<stdio.h>
int main ()
{
    int a,d,b,c=0,e=0;
    printf("Enter two no");
    scanf("%d %d",&a,&d);
    for(b=1;b<=a;b++)
    {
        if(a%b==0)
        c++;
    }
    for(b=1;b<=d;b++)
        {
            if(d%b==0)
            e++;
        }
    if (c==2 && e==2)
    printf("coprime no");
    else
    printf("Not a coprime no");
    return 0;
}



test for coprime nos



#include<stdio.h>
int main()
{
    int i,a,b,l=1;
    printf("Enter two numbers");
    scanf("%d %d",&a,&b);
    i=b>a?a:b;
    while(i>=2)
    {
      if(a%i==0 && b%i==0)
      {
        l=l*i;
        break;
      }
      else
      i--;
    }
    if(l==1)
    printf("coprime no");
    if(l>1)
    printf("not a Coprime no");
    return 0;
}



print all prime no till 100



#include<stdio.h>
int main()
{
    int a,b,c,e;
    for(b=1;b<100;b++)
    {
        e=0;
        for(c=1;c<=b;c++)
        {
            if(b%c==0)
            e++;
            
        }
        if(e==2)
        printf("%d ",b);
    }
    return 0;
}