Well.. in old days those notations wheres used to improve readability
of the code. The 'm' prefix means that this variable is a member variable
and therefore express the scope of the variable. There are various
variations like "m_" or just "_" that are used for the same purpose.
Some kind of standard notation used in old days is called the "Hungarian
notation" .. read HERE
the Wikipedia entry
Nowadays there is really no need anymore for those naming conventions.
We have code highlighting and all that fancy stuff in our IDEs that makes
those old notations unnecessary and render them useless.
In many cases when u read code today that uses notations they
are used wrong because someone saw them somewhere and thinks
"uuuh that looks Pro" and begins to use it no matter what.
The other cases i guess are old school coder that cant get rid of this habit