How to extract the decimal part from a floating point number in C?

Question

How can we extract the decimal part of a floating point number and store the decimal part and the integer part into two separate integer variables?

Answer 1

If you just want to get the first decimal value, the solution is really simple.

Here's an explanatory example:

int leftSideOfDecimalPoint = (int) initialFloatValue; // The cast from float to int keeps only the integer part

int temp = (int) initialFloatValue * 10;
int rightSideOfDecimalPoint = temp % 10;

Say for example we have an initial float value of 27.8 .

• By just casting the initial float value to an int, you discard the fraction part and only keep the integer part.
• By multiplying the initial float value by 10 we get a result of 278.0, then by casting this result to int, gives you the value of 278
• If we divide 278 by 10, we get 27.8, of which the remainder is 8, which is the value at the right side of the decimal point. Thus use modulus.

This technique can then be used to get the following decimal characters by using for example 100 instead of 10, and so on.

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Just take note that if you use this technique on real-time systems, for example to display it on a 7-segment display, it may not work properly because we are multiplying with a float value, where multiplication takes a lot of overhead time.