3 .


System programming involves designing and writing computer programs that allow the computer hardware to interface with the programmer and the user, leading to the effective execution of application software on the computer system. Typical system programs include the operating system and firmware, programming tools such as compilers, assemblers, I/O routines, interpreters, scheduler, loaders and linkers as well as the runtime libraries of the computer programming languages.

There are two categories of programs. Application programs (usually called just "applications") are programs that people use to get their work done. Computers exist because people want to run these programs. Systemsprograms keep the hardware and software running together smoothly. The difference between "application program" and "system program" is fuzzy. Often it is more a matter of marketing than of logic.

The most important systems program is the operating system. The operating system is always present when a computer is running. It coordinates the operation of the other hardware and software components of the computer system. The operating system is responsible for starting up application programs, running them, and managing the resources that they need. When an application program is running, the operating system manages the details of the hardware for it. For example, when you type characters on the keyboard, the operating system determines which application program they are intended for and does the work of getting them there.

Some embedded systems do not use an operating system, but run their programs directly on the processor.

Modern operating systems for desktop computers come with a user interfacethat enables users to easily interact with application programs (and with the operating system itself) by using windows, buttons, menus, icons, the mouse, and the keyboard. Examples of operating systems are Unix, Linux, Android, Mac OS, and Windows.