If you execute a program on your shell without & it remaining on the foreground.
If you want to put it in background without kill it you can do this:
The process will be suspended.
Then type on the console
and it let see you which process you have suspendend, on the left you can see  it is the number of your process.
Well, now you can type this on your console
and the process will continue to work
%1 is the number of your process saw in jobs command.