COMBINATION OPERATING SYSTEMS

As presented here, different types of operating systems are optimized, or at least largely geared toward serving the needs of certain specific environments. In practice, however, a given environment may not exactly fit any of the described molds. For instance, both interactive program development and lengthy simulation are often encountered in university computing centers. For this reason, some commercial operating systems provide a combination of the described services.

For Example, a time-sharing system may support interactive user while also incorporating a full-fledged batch monitor. This allows computationally intensive non interactive programs to be run concurrently with interactive programs. The common practice is assign low priority to batch jobs and thus to exccute batched programs only when the processor would otherwise be idle. In other words, batch processing may be used as a filter to improve processor utilization while accomplishing a useful service of its own. Similarly, some time-critical events, such as receipt and transmission of network data packets, may be handled in real-time fashion on systems that otherwise provide time-sharing services to their terminal user.