Programming is the process of writing instructions (a program) for a computer to use to solve a problem. These instructions must be written in a programming language. A program can be anything from a simple list of instructions that adds three numbers together to a large complex structure with many subsections, which calculates the payroll for a major corporation. Programs and series of programs are referred to as software. Some programs direct the computer in its own internal operations. These are called system programs. Other programs are written to solve users problems. They are referred to as application programs.
System programs directly affect the operation of the computer. They are designed to facilitate the efficient use of the computer's resources and aid in the development and execution of application programs. In early computer systems, human operators watched over computer operations, decided the order in which programs were run, and prepared the necessary input and output devices needed by a program. But as the processing speeds of CPUs increased, the speed of the human operators remained the same. Time delays and errors caused by human operators became a serious problem.
In the 1960s operating systems were developed to overcome this problem. An operating system is a set of system programs that allows system to manage its own operation if such a way that the system's resources are used efficiently.