P4-L7: non preemptive scheduling algorithms

first come, first served (FCFS)

Processes are scheduled in the order they arrive. Simple but can cause convoy effect

shortest job first (SJF)

Runs the process with the shortest burst time first. Optimal for waiting time, but can cause starvation.

turnaround time

completion time - arrival time

waiting time

turnaround time - burst time

priority scheduling (non preemptive)

Each process has a priority number.
Lower value = higher priority.
If two processes have the same priority, use FCFS.

starvation

When low-priority processes never get to run because higher-priority ones keep coming in

aging

A technique to prevent starvation by gradually increasing a process’s priority the longer it waits.

convoy effect

Occurs in FCFS when a long process delays all others, especially I/O-bound ones

Transitional Scheduling: SRTF

Shortest Remaining Time First – preemptive version of SJF, where a running process can be interrupted by a shorter one.

gantt chart

A timeline diagram showing when each process runs and when it finishes. Often used to calculate turnaround/waiting times.

ready queue

The list of processes that are ready to run but waiting for CPU time