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 log10()                 Calculate Base 10 Logarithm

 #include   <math.h>

 double     log10(x);
 double     x;                           Floating-point value

    log10() returns the base 10 logarithm of 'x'.

    Returns:    Base 10 logarithm of 'x'. If 'x' is negative, matherr()
                is called with a DOMAIN error, a DOMAIN error message is
                printed to 'stderr', 'errno' (defined in <stdlib.h>) is
                set to EDOM (defined in <math.h>), and the value negative
                HUGE_VAL (defined in <math.h>) is returned.  If 'x' is
                0.0, matherr() is called with a SING error, a SING error
                message is printed to 'stderr', 'errno' is set to ERANGE,
                and the value negative HUGE_VAL is returned.

      Notes:    Error handling can be modified with the matherr()
                routine.

 Compatibility: MSC version 4.0 set 'errno' to EDOM if 'x' was either 0.0
                or negative.

   -------------------------------- Example ---------------------------------

 The following statements calculate the base 10 logarithm of several values
 in an array and report any DOMAIN (negative arguments) or SING (0.0
 argument) errors.

           #include <math.h>   /* for log10(), SING, DOMAIN, exception*/
           #include <stdio.h>  /* for printf() */

                              /* 0.0 and -1.1e-5 cause errors */
           double value[5] = {100.1, 1.0e300, 0.0, 5.1e-99, -1.1e-5};
           main()
           {
               double base10_log;
               int i;

               for (i = 0;  i < 5;  i++) {
                   base10_log = log10(value[i]);
                   printf("base 10 logarithm of %e = %e\n",
                           value[i],base10_log);
               }
           }