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Since a Floating Point Unit (FPU) is not present in Arduino Uno, I wanted to know how float operations are performed. If it is simulated as integer operations, I want to know how exactly the simulation is done.

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    Floating point operations are implemented (rather than “simulated”) in software. You can disassemble any program using floats and see how it's done. – Edgar Bonet Sep 28 '17 at 7:19
  • Implementing floating point in software would mean breaking the number into its mantissa and exponent components (represented as integers) and performing arithmetic on them. Is this correct? – Sridhar Gopinath Sep 28 '17 at 8:21
  • Of course. The splitting is done by the function __fp_split3. – Edgar Bonet Sep 28 '17 at 8:34
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As I said in my comment, all float operations are implemented in software. As a simple test, I compiled the following program:

volatile float x, y, z;

int main(void)
{
    z = x + y;
    return 0;
}

The compiler translated the sum operation into a call to __addsf3. This function extends its arguments to flt40_t format (non-standard 40 bits float), calls __addsf3x to do the 40-bit addition, then calls __fp_round to convert the result into the standard float format. __addsf3x also makes a few library calls of its own. In the end, the addition pulled the following functions into the compiled program: __subsf3, __addsf3, __addsf3x, __fp_inf, __fp_nan, __fp_pscA, __fp_pscB, __fp_round, __fp_split3, __fp_splitA, __fp_zero and __fp_szero.

All these functions are provided by the avr-libc. You can find them in the libm/fplib directory. See for example the files:

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software emulation. The float is decomposed into sign, exponent and mantissa and then integer operations are used to do the actual math.

Addition and subtraction means shifting the mantissas to a common magnitude, adding/subtracting them and then checking the highest set bit for the new exponent.

Multiplication means adding the exponents and multiplying the mantissas. Division is subtracting.

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