C / C++ bootable program which reads file contents from a directory on the computer

C / C++ bootable program which reads file contents from a directory on the
computer

I want to create a program which can be stored on a CD or a flash drive.
This program should be able to read a file's content in a directory if
exist. For example, search the file "test" in the Linux Desktop Folder
which contains "123".
But how do I create such programs which can be directly started from the
BIOS? When I create a simple hello-world executable on linux it won't be
able to run on a non-linux-OS.
And will libraries such as stdio.h and stdlib.h even still be usable?