# Difference between float and double in C/C++

• Difficulty Level : Easy
• Last Updated : 08 Nov, 2022

To represent floating point numbers, we use float, double and long double. What’s the difference? double has 2x more precision than float. float is a 32-bit IEEE 754 single precision Floating Point Number – 1 bit for the sign, 8 bits for the exponent, and 23* for the value. 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. double has 15 decimal digits of precision. Let’s take an example: 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. Notice the difference in using float and double.

## CPP

 `// C program to demonstrate` `// double and float precision values`   `#include& lt; stdio.h & gt;` `#include& lt; math.h & gt;`   `// utility function which calculate roots of` `// quadratic equation using double values` `void` `double_solve(``double` `a, ``double` `b, ``double` `c)` `{` `    ``double` `d = b * b - 4.0 * a * c;` `    ``double` `sd = ``sqrt``(d);` `    ``double` `r1 = (-b + sd) / (2.0 * a);` `    ``double` `r2 = (-b - sd) / (2.0 * a);` `    ``printf``(" % .5f\t % .5f\n & quot;, r1, r2);` `}`   `// utility function which calculate roots of` `// quadratic equation using float values` `void` `float_solve(``float` `a, ``float` `b, ``float` `c)` `{` `    ``float` `d = b * b - 4.0f * a * c;` `    ``float` `sd = sqrtf(d);` `    ``float` `r1 = (-b + sd) / (2.0f * a);` `    ``float` `r2 = (-b - sd) / (2.0f * a);` `    ``printf``(" % .5f\t % .5f\n & quot;, r1, r2);` `}`   `// driver program` `int` `main()` `{` `    ``float` `fa = 1.0f;` `    ``float` `fb = -4.0000000f;` `    ``float` `fc = 3.9999999f;` `    ``double` `da = 1.0;` `    ``double` `db = -4.0000000;` `    ``double` `dc = 3.9999999;`   `    ``printf``("` `           ``roots of equation x2 - 4.0000000 x + 3.9999999` `           ``= 0 are` `           ``: \n & quot;);` `    ``printf``("``for` `float` `values: \n");` `    ``float_solve(fa, fb, fc);`   `    ``printf``("``for` `double` `values: \n");` `    ``double_solve(da, db, dc);` `    ``return` `0;` `}`

Output:

```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```

Let us see the differences in a tabular form that is as follows:

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