BleepingComputer.com: Help with C++

I decided to teach myself C++. I've been reading these tutorials :
http://www.cplusplus.com/doc/tutorial/variables/
But I don't understand this bit in the program :
"a = 5;
b = 2;
a = a + 1;
result = a - b;"
The answer is 4. I perfectly understood how you get 4, but I can't understand why it's done that way. Its very confusing writing the program like that.
Why do you actually need the first a = 5, if it might be easier to just write it as:
a = 6;
b = 2;
result = a - b;
I know it's probably a part of the language, but I want to know why it's done that way.

The application is just showing how variables can be assigned different values. In the real world, you would do it your way.

It's important to look at the equation as a time-frame.

You first declare a as 5.

And b as 2, which you understand.

When you see;

a = a - b

Think of it as:

new a (solution) = old a + old b

So a will have a new output and b will remain the same.

Hope i helped,

CrimsonSpider

It's basically showing you variable manipulation so you can see, at a basic level, how you can work with variables and manipulate them into other values.