Ensure that users can only access those files that are allowed. Of course, so far, the last important step in the development of operating system is to provide a standard graphical user interface (GUI) for programs. Although there is no technical reason why the operating system must provide these interfaces, operating system vendors always hope and encourage the software running on their systems to be consistent or similar to the operating system in appearance and behavior characteristics.
computer application
At first, huge and expensive digital computers were mainly used for scientific calculation, especially for military projects. For example, ENIAC was originally used.