Not very efficient interms of execution speed and memory utilization. Many high-level programs include assembly language routines. Don t need to worry about a particular CPU s instruction set. Must be translated into machine language. It is a special class of software, which keeps the hardware running efficiently and makes the process of communication with the hardware easy.
OS runs continuously whenever the computer is on and an application is running.
OS lies between the software application and the hardware. Communicating with the peripherals. Coordinating concurrently processing jobs. Resource monitoring, accounting and security. Program and data management.