Header files: #include <stdlib.h>
The function atof () is used to convert a string to a double-precision floating-point number (double) whose prototype is:
Double atof (const char* str);
The name of Atof () is derived from the abbreviation of the ASCII to floating point numbers, which scans the parameter str string, skips the preceding whitespace characters (such as spaces, tab indents, etc., which can be detected by the Isspace () function), The conversion is not started until a number or sign is encountered, and the conversion is ended with a non-numeric or string ending (' + '), and the result is returned. The parameter str string can contain a positive sign, a decimal point, or E (e) to represent an exponential portion, such as 123. 456 or 123e-2.
return value returns the converted floating-point number, or 0.0 if the string str cannot be converted to double.
Warm tip: ANSI C specification defines stof (), Atoi (), Atol (), strtod (), Strtol (), Strtoul () a total of 6 functions that can convert a string to a number, you can compare learning; use Atof () and use Strtod ( STR, NULL) results are the same. In addition in the C99/C++11 specification added 5 functions, namely Atoll (), Strtof (), Strtold (), Strtoll (), Strtoull (), do not introduce, please learn by yourselves.
Example:
#include <stdio.h> #include <stdlib.h>int main () { char *a = " -100.23", *b = "200e-2", *c = "341", *d = "100.34cyuyan", *e = "Cyuyan"; printf ("A =%.2f\n", Atof (a)); printf ("B =%.2f\n", atof (b)); printf ("c =%.2f\n", Atof (c)); printf ("D =%.2f\n", atof (d)); printf ("E =%.2f\n", Atof (e)); System ("pause"); return 0;}
Execution Result:
A =-100.23
b = 2.00
c = 341.00
D = 100.34
E = 0.00
C language Atof () function: Converts a string to a double (dual-precision floating-point number)
