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2013-10 2013-09 2013-08

atof - convert string to double in C

September 8, 2013 Posted by: GPA Views: 740 0 comments

Problem

Write simple program that convert string value to double and multiply it by 2.

Solution

In this article, you will learn how to convert a string value into double in C. In the given example we have used the library function atof() provided by the header file <stdlib.h>, to convert the input string into double value.

Declaration:

double atof(const char *inputString); 

where inputString is the string to be converted. 

This function converts its argument (a string) that represents a floating-point number—to a double value. It returns the double value. If the converted value cannot be represented—for example, if the inputstring is array of letters then the function atof is undefined.

Example:

   

#include <stdio.h>
#include <stdlib.h>//use this header for function atof
//this program prompt user to input string then convert this string to double and multiply by 2.
//main function
int main(int argc, char *argv[])
{
   char* inputString;//input string
   printf("globalproganswer.com\n");
   printf("Enter string (example 55.5): ");//promt the user to input string
   scanf("%s",&inputString);//read string from keyboard
   double inputValue=atof(&inputString);//convert inputString to double using function atof
   inputValue*=2;//multiply by 2.
   printf("The converted value multiply by 2 is %.3f.\n\n",inputValue);//show result
   system("PAUSE");  //delay
   return 0;//retun 0 exit program
}

Output

atof - convert string to integer in C

Download this example

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