CONTROL PROGRAMS
Control Programs are those programs which control & maintain the operation of computer. They provide basic facilities. Control program are further divided into further two categories
i). Initial program loader (IPL): it is essential part of an operating system. It is located permanently in the memory, which is called rom. It is also called resident routine. The basic purpose of IPL is to load other operating system program from secondary memory into the ram. Example:- when Computer is turned ON, then electronic chip is automatically activated & IPL read the boot sector routine (BSR), reside in the primary memory.
ii). supervisors programs: - A supervisory program or supervisor is a computer program, usually part of an operating system, which controls the execution of other routines. It regulates work scheduling, input/output operations, error actions, and similar functions and regulates the flow of work in a data processing system. In case of DOS the command.com is considered as supervisor and once loaded, it will remain all the time in memory while the computer is running.
iii) Job Controller: it is and important element of timesharing system. It recognizes job priorities and provides necessary steps to go from one program to the next. Example SJF (shortest job first)