Spring 2011»CSCI 340 Homework 3

CSCI 340 Homework 3

Assigned Date: Monday, Mar. 21, 2011
Due Date: Wednesday, Mar. 30, 2011
Due Time: 11:50am

Last modified on March 25, 2011, at 04:18 PM (see updates)

This is a solo assignment. You must work alone.


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

  • To gain experience using C file I/O, linked lists
  • To gain experience with process management


Create a process management simulation in C that implements a First Come First Serve (FCFS) scheduler.

Read in process information from an ASCII file. The name of the file will be provided as input to your program, using C command-line arguments.

int main(int argc, char *argv[])
   // argc equals the number of arguments received
   // argv is an array containing all command line arguments
   // argv[0] is set to the name of the program

For example, see [1].


Each line of the input file will contain 3 integers describing a single process to be run. The first integer is the process ID, the second integer is the arrival time of the process, and the third integer is the required execution time of the process (remember, we are simulating execution). You should ignore anything past the third integer on each line (e.g., we may use this feature to implement input-file comments). The file may contain an arbitrary number of processes.

Example file contents:

0 1 4    # first process has ID=0, arrives at second 1, and will execute in 4 seconds
1 3 2    # ...
2 6 7

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.

struct PBR
   int processID;
   int processArrivalTime;
   int remainingRunTime;
   struct PBR *next;          // a pointer to the next PBR in the queue (i.e. linked list)

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

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

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


Your program should deallocate all the space it allocated. A good strategy is to deallocate the PBR of any process that has completed. Also, depending on how you implement your linked list, you may also use a function called cleanUp(), which takes as argument(s) the program's dynamic data structure(s). It should be called before the program exits.

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.


For now, implement First Come First Serve (FCFS) to allocate the CPU to the processes. There will be no time quantum/slice, therefore the implemented algorithm will be non-preemptive.


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

average wait time: x

average turnaround time: y

average execution time: z

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.


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." [2]

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. Remove the angle brackets!)

   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

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. Cprogramming.com, Accepting command line arguments, accessed on-line, March 20, 2011.
  2. Cooper, D. and Clancy, M. (1985) "Oh! Pascal", 2nd ed., W.W. Norton & Company, New York, p. 42.