Why comparing float gives unexpected output in C?

Question

See the following code

void main(){
   float a=5.2;
  if(a==5.2)
     printf("Equal");
  else if(a<5.2)
     printf("Less than");
  else
     printf("Greater than"); 
}

Expected output is equal but we does not get same why?

Answer 1

Use any of the below statements, it would work fine --
if ( a == (float) 5.2 )
OR
if ( a == 5.2f )

You need to inform the compiler that you are trying to compare 2 float numbers so you need to typecast it (explicit/implicit).

You can also try this --> float a= 5.2;
float b = 5.2;

Now compare them -- if (a == b ). This would also work fine

Answer 2

Floating point numbers are never stored in the exact form, these are stored in the form of exponent and manteesa form.

bit  31 30    23 22                    0
     S  EEEEEEEE MMMMMMMMMMMMMMMMMMMMMMM

now you can guess why if(a==5.2) is not equal because of they may have different value at some time :)

Comments

It's called IEEE 754 method

Answer 3

Try long double, more precise than float

Answer 4

a is float variable so it compare only float value like a=5.2 so a compare its float value i.e a=.2
.2<5.2
answer is less than
and when if(a==(float)5.2)
answer is equal.