processScheduler

What is Process Scheduling

According to TutorialsPoint, The Process Scheduling is the activity of the process manager that handles the removal of the running process from the CPU and the selection of another process on the basis of a particular strategy.

Process scheduling is an essential part of a Multiprogramming operating systems. Such operating systems allow more than one process to be loaded into the executable memory at a time and the loaded process shares the CPU using time multiplexing.

Behavior

This C project implements 4 kinds of scheduling algorithms using a stack and two priority queues. These algorithms are:

• First Come First Served (FCFS) - used for batch systems (we want productivity).
• Shortest Job First (SJF) - used for batch systems (we want productivity).
• Round Robin - cyclic executive - used for interactive systems (we want fairness).
• Round Robin - with priorities - used for interactive systems (we want fairness).

Lets call quantum = how many ticks a process needs to be completed. We will define a tick later. The program reads commands from an input_file and writes output to another file.

Commands

The implemented commands are the following:

• t - tick, time passes
• a name x y - add a new process named name that has quantum x and priority y
• ma name1 x1 y1 name2 x2 y2 ... multiple add, the same meaning as add but with more processes
• w - wait, the RUNNING process goes to WAITING
• e name - event, an event wakes process name from WAITING
• s - show, prints info about the RUNNING process: name_of_the_process quantum_of_current_process

After the following commands, an implicit t is executed: a, ma, w, e.

About the input_file

The input_file has the following form:
1 / 2 / 3 x / 4 x y / 5 x y
command1
command2
command3
...

where 1/2/3/4/5 are the type of scheduling algorithms used:

• 1 = FCFS, 2 = SJF 3 = RR - cyclic executive, 4 = RR - with priorities, 5 = RR - with dynamic priorities (dynamic means that the scheduler can update the priorities in time).
• x = quantum and y = the number of priority levels

How to run it

1. Compile planificator.c using make or your favourite compiler.
2. Write your input_file. You can find an example in fisier1.
3. Run your program and don't forget to mention input_file and output_file.
   ./planificator input_file output_file
4. Remember, all the output will be written into the output_file you specified inside the command.

Have fun and keep on coding! :)