Chapter 7 - Introduction to multitasking

Abstract

Most complex real-time systems require a number of tasks (or programs) to be processed at the same time. For example, consider an extremely simple real-time system that is required to flash an LED at required intervals, and at the same time look for a key input from a keyboard. One solution would be to scan the keyboard in a loop at regular intervals while flashing the LED at the same time. Although this approach may work for a simple example, in most complex real-time systems a multitasking approach should be implemented. The term multitasking means that several tasks are processed in parallel on the same CPU. In a multitasking system, several tasks to run on a single CPU at the same time. Therefore, task switching is done where the tasks share the CPU time. In many applications, tasks cannot run independently of each other and they are expected to cooperate in some way. For example, the execution of a task may depend upon the completion of another task. This chapter describes briefly the various scheduling algorithms used in practice and gives their advantages and disadvantages.