While looking at your account one day you may notice a file called core. It will probably be a very big file and you won't remember creating it. That's because you didn't; core files, also called core dumps, are generated when a program crashes. The application dumps everything in its memory to the core dump so you can go through it, figure out what's wrong and debug the program.
To do this, type file ~/core to check which executable created the dump, then
gdb <executable> <core file> to enter the debugger. Type where to get a stack trace.
You can limit the size of the core dumps by putting ulimit -c <size> in your .profile if you use a Bourne-type shell, or limit coredumpsize <size>
in your .login if you use a C-type shell. If you set the size to 0, no core files will be generated.