strtod, atof

Purpose

     Converts an ASCII string to a floating-point number.

Library

     Standard C Library (libc.a)

Syntax

       double strtod (nptr, ptr)                 double atof (nptr)
       char *nptr, **ptr;                        char *nptr;
     Description

     The  strtod  and  atof subroutines  convert  a  character
     string, pointed  to by the  nptr parameter, to  a double-
     precision floating-point number.   The first unrecognized
     character ends the conversion.

     These subroutines  recognize a character string  when the
     characters appear in the following order:

     1.  An optional string of white-space characters
     2.  An optional sign
     3.  A string  of digits  optionally containing  a decimal
         point
     4.  An optional e  or E followed by  an optionally signed
         integer.

     If  the string  begins  with  an unrecognized  character,
     strtod and atof return the value 0.

     If the value of ptr is not (char **) NULL, then a pointer
     to the  character that terminated  the scan is  stored in
     *ptr.  If  an integer  cannot be formed,  *ptr is  set to
     nptr, and 0 is returned.

     If the  correct return  value overflows, strtod  and atof
     return INF.  On underflow, strtod and atof return 0.

     The atof  (nptr) subroutine call is  equivalent to strtod
     (nptr, (char **) NULL).

     The strtod and atof  subroutines perform conversions to a
     floating-point  number.   See  "strtol, atol,  atoi"  for
     information on conversions to integers.

     Related Information

     In this book:  "scanf, fscanf, sscanf, NLscanf, NLfscanf,
     NLsscanf" and "strtol, atol, atoi."