I know what it is: Mathcad and Mathcad Prime!

[ValeryOchkov]

Correct names Mathcad and Mathcad Prime are Mathcad and Mathcad Jr.

There are a Father and a Son.

The Father is much more experienced than his Son, but the Father had a career coming to an end.

The Son can not yet do much of what his father could do.

But the son gradually from perenemaet experience of his father and learns a lot what you do not know the father.

Yet there is the illegitimate son - SMath.

[LucMeekes]

The prime symbol is often used in mathematics to denote a derivative, so Mathcad and Mathcad Prime can be viewed of as:

An interesting notion is that derivatives exhibit a form of instability, a good example of which is found in trading stock where options deal with changes in share value over time: the derivative over time. While trading in shares can be viewed of as relatively safe, trading in options is much more dangerous: you can win, but you can also loose much money in a short time.

A bit closer to technology: observe the derivative of a step, which is a big spike, the derivative of which is 2 spikes etc.

All this does not mean I had rather they'd integrate Mathcad: I like Mathcad as it was, stand-alone, broad and powerfull.

[ValeryOchkov]

OK

But what is it the argument

[LucMeekes]

Here's my first thought:

Mark the positions of the parentheses!