A program or group of programs designed for end users. Software is often divided into two categories:
Operation System (O/S)The most important program that runs on a computer. Every general-purpose computer must have an operating system to run other programs. For large systems, the operating system has even greater responsibilities and powers. It makes sure that different programs and users running at the same time do not interfere with each other. The operating system is also responsible for security, ensuring that unauthorized users do not access the system.
Applications software sits on top of systems software because it is unable to run without the operating system and system utilities. For example: