Difference between float and double in C/C++
For representing floating point numbers, we use float, double and long double.
What’s the difference ?
double has 2x more precision then float.
float is a 32 bit IEEE 754 single precision Floating Point Number1 bit for the sign, (8 bits for the exponent, and 23* for the value), i.e. float has 7 decimal digits of precision.
double is a 64 bit IEEE 754 double precision Floating Point Number (1 bit for the sign, 11 bits for the exponent, and 52* bits for the value), i.e. double has 15 decimal digits of precision.
Let’s take a example(example taken from here) :
For a quadratic equation x2 – 4.0000000 x + 3.9999999 = 0, the exact roots to 10 significant digits are, r1 = 2.000316228 and r2 = 1.999683772
roots of equation x2 - 4.0000000 x + 3.9999999 = 0 are : for float values: 2.00000 2.00000 for double values: 2.00032 1.99968
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