I'm a computer science graduate with interest in mathematics, and I'm trying now to read some textbooks as self learning.
I want to read about the extension of natural numbers to integers, fractions, real numbers and up to the complex numbers. I thought this belongs to abstract algebra, but I read the table of contents of some abstract algebra books and it contained nothing about that.
So what field of mathematics should I study to understand these issues? I always wanted to really understand complex numbers for example, but I'm not sure where to start. Is it complex analysis, abstract algebra or what?