gcc/++ update (newbie)

[spamse]

I have installed packages for gcc/++ 3.3.5, and have just got the
packages for 4.0. I want to be using the newer version, but 3 is the
default. I realise that it is possible to specify on the command line
which version, but can I not remove the older one? Synaptic tells me
that it will have to remove half of my software that depends on it if
I try!

Also, I am attempting to compile a simple C++ program. It is a simple
text-book header that compiles fine, and code to create an object. I
get this error from the command line (from g++ 3.3.5):

spamse at spamson:~/Docs/Development/Workspace/Stocks$ g++ Stock.cpp
/usr/lib/gcc-lib/i486-linux/3.3.5/../../../crt1.o(.text+0x18): In
function `_start':
../sysdeps/i386/elf/start.S:98: undefined reference to `main'
collect2: ld returned 1 exit status

It appears to be some dependency issue, but I am clueless as to how to
solve it. I have checked that I have the gcc standard libraries
installed, as far as I can tell.

Sam