Is it right output of C programe -

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possible duplicate:
floating point comparison

i have simple c code , output comes out unexpected me

main()  {    float f1 = 1.0;    double f2 = 1.0;    if(f1==f2)   printf("equal");   else    printf("unequal");    }

i expecting output "unequal" output equal .why so?

since float , double have different precision ,output should unequal.

precision matters when number can't represented exactly. since both floats , doubles (being ieee 754 single , double precision values) can represent 1.0 exactly, precision doesn't come it.

1.0 0 sign bit, exponent bits except highest set 1, , no mantissa bits set. in single precision, that's binary:

0-01111111-00000000000000000000000

and, double precision:

0-01111111111-0000000000000000000000000000000000000000000000000000

not numbers representable in ieee 754 - example, 1.1 mention in comment stored 1.100000023841858 in single precision.

have @ this answer example of decoding floating point value.

harald schmidt's online single-precision converter excellent site play around if want understand formats. liked much, made desktop version in case ever disappeared (and capable of doing double precision well).


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