Real-Time Operating Systems (RTOS) currently available in industry, for embedded systems, require multitasking support in the targeted processor. The category of such operating systems is known as Pre-emptive Multitasking Kernels. However multitasking support is not provided by all processors. We have developed multitasking scheduling technique (Collaborative Multitasking) for the processors or microcontrollers which do not have built-in multitasking support such as support for context switching, for example, 89C51 Microcontroller and 89C52.