Operating Systems — common mistakes

In exam questions about memory management, be precise with your terminology. Distinguish clearly between 'paging' (fixed-size, non-contiguous, OS-level) and 'segmentation' (variable-size, logical units, programmer's view). For scheduling, always show your working clearly, for example by using a Gantt chart or a step-by-step trace of the ready queue.

An Operating System is essential system software that manages the entire computer system. Utility software, on the other hand, is designed to perform a specific maintenance task to help manage, analyse, configure, or optimise the computer. Examples include antivirus software, disk defragmenters, and file compression tools. Utilities often work alongside the OS but are not part of its core functionality.

No, the BIOS (Basic Input/Output System) is not part of the OS. The BIOS is firmware stored on a chip on the motherboard. Its primary job is to initialise the hardware during the booting process (the 'power-on self-test' or POST) and to load the operating system from the storage drive into RAM. The OS takes over control from the BIOS once it has loaded.

Different scheduling algorithms are designed to optimise for different system goals. For example, First-Come, First-Served (FCFS) is simple and fair but can be inefficient if a long process makes short ones wait. Round Robin (RR) is designed for time-sharing systems to ensure responsiveness for all users. Shortest Job First (SJF) is optimal for minimising average waiting time but is difficult to implement in practice. The choice of algorithm depends on the type of system (e.g., batch, interactive, real-time) and its performance objectives.