how to make negative numbers into positive

Question

I am having the negative floating point number as:

a = -0.340515;

to convert this into positive number I used the abs() method as:

Answer 1

floor a;
floor b;
a = -0.340515;

so what to do?

b = 65565 +a;
a = 65565 -b;

or

if(a < 0){
a = 65565-(65565+a);}