| Date | November 2018 | Marks available | 3 | Reference code | 18N.1.HL.TZ0.7 |
| Level | HL | Paper | 1 | Time zone | no time zone |
| Command term | Distinguish | Question number | 7 | Adapted from | N/A |
Question
Distinguish between the use of time slicing and priorities in the scheduling of processes by an operating system.
Markscheme
Award [3 max].
Prioritizing enables execution of the (highest priority) process until a higher priority task enters;
The OS/scheduler put processes (jobs) in the right place in a queue in order of priority (accept examples, an I/O operation has higher priority than calculations because it uses less CPU time);
Time slicing allows process to execute for a fixed time/each process is given a fixed period of time (time slice) for which the process is allowed to run/;
The scheduler is run once every time slice to choose the next process to run;
Note: Award [1 max] if evident that the scheduler software is responsible for organizing all of the processes that need servicing/responsible for looking at what resources are available (CPU time and peripheral devices) /responsible for making decisions about what order to put all the processes in (when to start any particular process, and when to finish it);
