An application is an executable program which is provided data in the form of
- information included in its source code
- passed to it by the user running the program as input
- information given as command parameters or operating system values
- read from a data file
Even the ubiquitious "Hello World" example program contains data, in the form of the output string. All application programs that perform any useful work have some form of data, either stored in the program or obtained from an external source (such as the operating system, the user or a file).
Applications are the programs which people use to do things on a computer system, even if the application is included as part of the operating system. They are distinguished from the general underlying operating system which runs the computer directly. Thus it can be said that all applications are programs, but not all programs are applications.