Question

how to make a bootable software?

Will be a simple command prompt where I can access my harddisk (may be windows or linux command).
Nothing else, is it possible?

Answer 1

You're talking about writing assembly code to control the hardware and software by yourself. It's not impossible, but very tedious.
There are softwares that let you bundle the software you want and assemble them into a bootable disk, however if you're talking about making an OS, take a look at the Linux Kernel's source code.