Hi all. I am new to C, at least to the concept of pointers. I am trying to write a process scheduling simulator for my operating systems class (at the last minute of course). Anyway, I wrote a program just using arrays and got it to compile but then of course I got a Segmentation Fault so I am trying to start fresh using pointers. Right now, all I want to do is take the input file and add the pieces of input into structs (this part works) but then when I add a for loop to go through the structs again and increment values, etc. I get another segmentation fault. Here is the code:
#include <stdio.h>
#include <stdlib.h>
int p, clock;
int addition, numJobs;
int i, j, availableMem;
// Enum, structure declarations
enum state {
NOTARRIVED,
NOTINSYSTEM,
READYTORUN,
SLEEPINGIO,
RUNNING,
EXITED
} currentState;
/*******************************************************
For each process:
unique PID, arrival time, service time, priority rating,
memory allocation, no start, time in IO state,
time in Ready to Run state, time in Running state,
timeslice
*******************************************************/
typedef struct
{
int pid;
int arrivalTime;
int serviceTime;
int priorityRating;
int memoryAllocation;
int noStart;
int timeInIO;
int timeInReadytoRun;
int timeslice;
int memTaken;
enum state currentState;
} process;
typedef struct
{
process elems[1000];
int back; // Initialized to -1
int front; // Initialized to 0
} queue;
/* Input processes from data file into array of structs:
Process ID : Arrival Time : Service Time : Priority : Memory Requirement in MB */
process *proc[20];
/* Priority Queues: 0, 1, 2, 3, 4, I/O queue, Not In System queue. */
queue queue0, queue1, queue2, queue3, queue4, queueIO, queueNoMem;
/* Begin Main */
int main(int argc, char *argv[0])
{
char line[80];
FILE *inputFile, *outputFile;
inputFile = fopen("input_file.txt", "r");
if (inputFile == NULL)
{
fprintf(stderr, "Can't open input file!\n");
exit(1);
}
outputFile = fopen("output_file.txt", "w");
if (outputFile == NULL)
{
fprintf(stderr, "Can't open output file!\n");
exit(1);
}
p = 0;
clock = 0;
fprintf(outputFile, "Input File: \n");
while(fgets(line, 80, inputFile))
{
int uniquePID, arriveTime, serviceTime, priority, memAlloc;
sscanf(line, "%d : %d : %d : %d : %d", &uniquePID, &arriveTime, &serviceTime, &priority, &memAlloc);
proc[p] = (process *)malloc(sizeof(process));
proc[p]->pid = uniquePID;
proc[p]->arrivalTime = arriveTime;
proc[p]->serviceTime = serviceTime;
proc[p]->priorityRating = priority;
proc[p]->memoryAllocation = memAlloc;
proc[p]->noStart = 0;
proc[p]->timeInIO = 0;
proc[p]->timeInReadytoRun = 0;
proc[p]->timeslice = 0;
proc[p]->currentState = NOTARRIVED;
// LATER -> free(proc[p]);
addition = proc[p]->memoryAllocation%4;
proc[p]->memTaken = proc[p]->memoryAllocation + addition;
fprintf(outputFile, "PID = %d Arrival Time = %d Service Time = %d Priority = %d Memory Needed = %d \n",
proc[p]->pid, proc[p]->arrivalTime, proc[p]->serviceTime, proc[p]->priorityRating, proc[p]->memoryAllocation);
p++;
}
// Set total number of jobs
numJobs = p;
fprintf(outputFile, "Number of jobs: %d \n", numJobs);
// Set memory size for entire simulation
availableMem = 32;
fprintf(outputFile, "Available Memory: %d \n", availableMem);
// THIS IS WHERE I THINK THE SEGMENTATION FAULT OCCURS
// WHEN I TRY TO ACCESS THE PIECES IN THE STRUCTS
// Add new incoming jobs to the "Ready to Run" state
for(i = 1; i <= numJobs; i++)
{
if(availableMem > proc[i]->memTaken)
{
// Allocate necessary memory for this process
availableMem = availableMem - proc[i]->memTaken;
// Set the state to Ready to Run
proc[i]->currentState = READYTORUN;
}
else
{
// Keep this job out of the system until
// more memory is available
proc[i]->currentState = NOTINSYSTEM;
proc[i]->noStart++;
}
}
}
Unsolved 
