know the return value of a native (c) program in linux

Hi folks
use this command:
echo $?
to know the return value of a native program in Linux.
try it yourself:

scenario 1:

more 
echo $?  #(watch the result, it will be 1, which means unsuccess)

scenario 2:

echo "hello world" > file
more file
echo $?  #(watch the result, it will be 0, means success)