C/math.h/log10

    
//Declaration: float log10f(float num); 
               double log10(double num); 
               long double log10l(long double num);  
 
    
  
  #include <math.h>
  #include <stdio.h>
  int main(void)
  {
    double val = 1.0;
    do {
      printf("%f %f\n", val, log10(val));
      val++;
    } while (val<11.0);
    return 0;
  }
         
/*
1.000000 0.000000
2.000000 0.301030
3.000000 0.477121
4.000000 0.602060
5.000000 0.698970
6.000000 0.778151
7.000000 0.845098
8.000000 0.903090
9.000000 0.954243
10.000000 1.000000
*/