Why the value of any float was changed after store in a variable .. in all languages

Question

#include <stdio.h>

int main() {
float a=.1;
printf("%.17f",a); // here .1=.10000002983342983
printf ("%.17f",.1);//here .1 =.100000000000001
return 0;
}

Answer 1

A floating point literal such as that .1 you used as second argument in the second printf() call, is expressed as `double` type.

Precision difference between `float` and `double` is the reason why you're seeing those different outputs. Variable <a> is of `float` type, the literal .1 is of `double` type.

You either define <a> as `double`, which means <a> and literal .1 are of the same type. Or you can explicitly specify the literal .1 as a `float` type by adding 'f' suffix to its value as follows ...

printf( "%.17f", .1f ); // <-- notice the 'f' suffix