C atof() function

C atof() function - Convert character string to float

The atof() function is used to convert a character string to a double-precision floating-point value.

Syntax:

double atof(const char *str)

Parameters:

Return value from atof()

• Returns a double value that is produced by interpreting the input characters as a number.
• If the function cannot convert the input to a value of that type return value is 0.

Example: atof() function

The following example shows the usage of atof() function.

#include <stdlib.h>
#include <stdio.h>
 
int main(void)
{
    double x;
    char *s;
 
    s = "-3423.12E-15";
    printf("String value: %s",s);
    x = atof(s);   
    printf("\nDouble-precision floating-point value = %.4e\n",x);
    s = "+3423.12E-15";
    printf("\nString value: %s",s);
    x = atof(s);   
    printf("\nDouble-precision floating-point value = %.4e\n",x);
    s = "3423.12E-15";
    printf("\nString value: %s",s);
    x = atof(s);   
    printf("\nDouble-precision floating-point value = %.4e\n",x);
    s = "4567.456";
    printf("\nString value: %s",s);
    x = atof(s);   
    printf("\nDouble-precision floating-point value = %.4e\n",x);
    s = "4567";
    printf("\nString value: %s",s);
    x = atof(s);   
    printf("\nDouble-precision floating-point value = %.4e\n",x);
}

Output:

String value: -3423.12E-15
Double-precision floating-point value = -3.4231e-012

String value: +3423.12E-15
Double-precision floating-point value = 3.4231e-012

String value: 3423.12E-15
Double-precision floating-point value = 3.4231e-012

String value: 4567.456
Double-precision floating-point value = 4.5675e+003

String value: 4567
Double-precision floating-point value = 4.5670e+003

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