We call these the resource and beautification principles respectively.
Resource is a commodity needed to get work done.
An operating system is a program that might be likened to a computer's consciousness, turning a set of chips and circuit boards into a working brain, able to respond to instructions. Applications software is put in after the operating system to make the computer perform specific tasks, like processing words, constructing spreadsheets, or doing income taxes. Layers of a System Also look at picture from Tanenbaum's book. Processes Processes are hard to define precisely and exact definitions are usually operating system specific. A program is a set of data and code that manipulates it.