Bill Manaris : Spring 2012 / CSCI 340 Homework 3

Assigned Date: Wednesday, Mar. 14, 2012
Due Date: Friday, Mar. 30, 2012
Due Time: 10:50am

Last modified on March 26, 2012, at 12:15 PM (see updates)

NOTE: This homework is an extension of homework 2. Verbiage from homework 2 is included here to make this assignment self-contained. The extension involves adding more scheduling algorithms (Shortest-Job-First, Round Robin, and Shortest-Remaining-Time First). It also slightly changes the format of the input data.

This is a pair-programming assignment (i.e., you may work with one partner). You may discuss the assignment only with your partner or the instructor/grader.


This assignment focuses on Process Management with C, and in particular:


Create a process management simulation in C that implements a First-Come-First-Serve (FCFS), Shortest-Job First (SJF), and Round-Robin (RR), Shortest-Remaining-Time First (SRTF) scheduling algorithms.

Read in process information from the standard input.


Input has the following format:

2        # CPU quantum (ignored by non-preemptive schedulers)
3        # number of processes to schedule
0 1 4    # first process has ID=0, arrives at second 1, and needs 4 secs of CPU time
1 3 2    # ...
2 6 7

You should ignore anything past the valid data on each line (e.g., comments). The file may contain an arbitrary number of processes.

You may only assume that processes are sorted by arrival time.


Processes and their related information should be stored in ProcessBlockRecords (PBR) organized as a queue in order of their arrival time. The PBRs should be represented as C structs, and the queue as a linked list or an array.

Below is an example struct for the PBR. Depending on the scheduling algorithm, your struct may require additional fields - be sure to document the rationale for your changes/additions. The same data structure should be used for all algorithms.

struct PBR
   int processID;
   int processArrivalTime;
   int remainingRunTime;

To allocate space for the C structs use malloc(). For example:

struct PBR *process = (struct PBR *)malloc(sizeof(struct PBR));

To deallocate the space use free(). For example:


Your program should deallocate all the space it allocated.

Instead of maintaining actual time in your program, you should use a counter and treat every increment made as the passing of 1 second.

In a real system, each process would perform some sort of work while executing, but, for simplicity, this simulation will omit this detail.

Modularize your design using meaningfully named functions.


For this assignment, you will be implementing four separate scheduling algorithms (each in its own file).

Implement the following scheduling algorithms:

Also submit a schedule.h file with common data structures and function prototypes and definitions.

No global variables allowed. Everything needed by a function should be passed via its parameter list. Functions that make updates, should return the modified values (so, aim for functions that modify one array, or one variable, at most).


Your program should output the following for each process:

Process n was allocated the CPU at time p seconds.
Process n completed at time q seconds.

where n, p, q are int values.

Upon completion of the simulation, i.e., when all processes have finished executing, your program should output the following statistics:

Simulation Statistics:

Average wait time: x seconds
Average turnaround time: y seconds
Average execution time: z seconds

where x, y, z are float values.

Average wait time: Average (across all processes) of elapsed time between a process' arrival time and the moment it is allocated the CPU.

Average turnaround time: Average (across all processes) of elapsed time between a process' arrival time and its completion.

Average execution time: Average of all the processes' run times.

So, for the above input example, the output should be:

Process 0 was allocated the CPU at time 1 seconds.
Process 0 completed at time 5 seconds.
Process 1 was allocated the CPU at time 5 seconds.
Process 1 completed at time 7 seconds.
Process 2 was allocated the CPU at time 7 seconds.
Process 2 completed at time 14 seconds.

Simulation Statistics:

Average wait time: 1.0000 seconds
Average turnaround time: 5.3333 seconds
Average execution time: 4.3333 seconds


Follow the Golden Rule of Style: "A program should be as easy for a human being to read and understand as it is for a computer to execute." [1]

In general, you should comment any variable, obscure statement, block of code, etc. you create.

Also, you should comment why something is being done, e.g.,

numStudents += 1;   /* we have processed one more student */

as opposed to how it is done, e.g.,

numStudents += 1;   /* increment numStudents by one */

Finally, your code should always include opening comments as follows.

(NOTE: Angle brackets signify information that needs to be filled out. In your final assignment, remove the angle brackets and the instructions included in them!)

   Author:     <Your Name(s)>
   Email:      <Your email address(es)>
   Class:      CSCI 340, Section 1
   Assignment: HMWK3
   Due Date:   <The assignment's due date>

   Certification of Authenticity <remove one of the following>:     

      I certify that this lab is entirely my own work.

      I certify that this lab is my own work, but I received
      some assistance from <Name(s)>

   TASK:   <Provide a simple, yet complete description of the task being
           performed by this program. It may be several sentences long.>

   INPUT:  <Describe the input to this program.  Be thorough.>

   OUTPUT: <Describe the output to this program.  Be thorough.>




You will submit your assignment via the stono submit command, as follows:

% submit csci340 hmwk3 fcfs.c sjf.c rr.c srtf.c schedule.h

where schedule.h contains common data structure and function prototypes and definitions shared by all programs.

No other submission mechanism will be accepted (e.g., email).


Your assignment will be graded based on the documentation, formatting, and correctness of your source code. Also the completeness / thoroughness of your work, and how well you followed the homework instructions.


  1. Cooper, D. and Clancy, M. (1985) "Oh! Pascal", 2nd ed., W.W. Norton & Company, New York, p. 42.
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