I have downloaded the c++ compiler from MinGW also set the environment variables
'<' and '>' are research characters for redirection and are not to be used in file names.
most likely in this case it is trying to read input from hello_world as it would be seeing < hello_world
but not find the file
The > p.cpp
would be attempting to write any output to p.cpp, so may have replaced what you had in that file.