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Why comparing float gives unexpected output in C?

+3 votes

See the following code

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

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

posted May 22, 2015 by Mohammed Hussain

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4 Answers

+2 votes

Use any of the below statements, it would work fine --
if ( a == (float) 5.2 )
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 May 25, 2015 by Ankush Surelia
+1 vote

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

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

answer Aug 3, 2015 by Salil Agrawal
It's called IEEE 754 method
0 votes

Try long double, more precise than float

answer May 23, 2015 by Amit Kumar Pandey
0 votes

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

answer Aug 2, 2015 by Vikram Singh
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