Question

Could someone point out the logical error in this code?

The code seems to start at the last input. But I want the code to output something like this:

Enter name: A
Enter time:5
Enter name:B
Enter time: 4
Enter name: C
Enter time:3
Enter name:D
Enter time: 9
Enter name: E
Enter time: 11
A process is started and ends in 5 sec.
1 sec passed...
2 sec passed...
3 sec passed...
4 sec passed...
5 sec passed...
B process is started and ends in 4 sec.
1 sec passed...
2 sec passed...
3 sec passed...
4 sec passed...
C process is started and ends in 3 sec.
1 sec passed...
2 sec passed...
3 sec passed...
D process is started and ends in 9 sec.
1 sec passed...
2 sec passed...
3 sec passed...
4 sec passed...
5 sec passed...
6 sec passed...
7 sec passed...
8 sec passed...
9 sec passed...
E process is started and ends in 10 sec.
1 sec passed...
2 sec passed...
3 sec passed...
4 sec passed...
5 sec passed...
6 sec passed...
7 sec passed...
8 sec passed...
9 sec passed...
10 sec passed...

10 sec reduced in E process with time left 1 sec.

E process is started and ends in 1 sec.
1 sec passed...
All Processes are executed...

Code:

#include 
#include 
#include 
#include 
#include 
#define S 4

typedef struct
{
   char pname [S];
   int ptime;
}PROCESS;

typedef struct
{
   PROCESS queue [S];
   int front;
   int rear;
}QUE;

void createQueue(QUE *);
void enCQueue(QUE *, PROCESS);
PROCESS deCQueue(QUE *);
bool isCEmpty(int,int);
bool isCFull(int,int);
void tshareProc (PROCESS);

int main(void)
{
   PROCESS p;
   QUE q;
  
   createQueue (&q);
   enCQueue (&q, p);
   tshareProc(p);
  
   return 0;
}

void createQueue(QUE *q)
{
   memset(q->queue,'\0',S);
   q->front = 0;
   q->rear = 0;
}

void enCQueue(QUE *q, PROCESS p)
{
   q->queue[q->rear] = p;
   q->rear = (q->rear + 1) % S;
}

PROCESS deCQueue(QUE *q)
{
   PROCESS p;
   q->queue[q->front]= p;
   q->front = (q->front + 1) % S;
   return;
}

bool isCEmpty(int front,int rear)
{
   if(front == rear)
       return true;
   else
       return false;
}
void tshareProc (PROCESS p)
{
   QUE q;
   int i, j, x;
   bool empty, full;
   createQueue (&q);

   for (i=0; i <= S; i++)
   {
  
       printf ("Enter username:");
       scanf("%s",&p.pname);
       printf("Enter time in seconds:");
       scanf("%d",&p.ptime);
       while(p.ptime < 1) {
       printf("Time must be greater than zero. \nInput again:");
       scanf("%d",&p.ptime);
       }
       enCQueue (&q,p);
   }
  
   empty = isCEmpty (q.front, q.rear);
   while (!empty)
   {
       if (p.ptime <= 10){
           printf ("\n %s's process is starting and will end in %d seconds \n", p.pname, p.ptime);
       for (j=0; j < p.ptime; j++){
           printf(" %d seconds passed\n",j+1);
           Sleep(1000);                             //change to sleep(1000) if giving error
           } //end of for loop
       deCQueue (&q);
       }
       else
       {
           printf("\n %s's process is starting and ends in 10 seconds\n",p.pname);
           for(x = 0; x < 10; i++) {
               printf("%d seconds passed\n",x+1);
               Sleep(1000);                         //change to sleep(1000) if giving error
           } // end of for loop
       p.ptime = p.ptime - 10;
       printf("10 seconds is subtracted in %s's process with %d seconds left\n",p.pname,p.ptime);
       deCQueue(&q);
       }
       enCQueue(&q, p);
   } //end of while loop
   printf ("All processes were performed");
   return;
}

Answer 1

Following is the fixed code, containing comments for fixes appropriately :

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <stdbool.h>
#include <stdint.h>
#include <unistd.h>

/*
 * We should be able to hold maximum 5 processes.
 */
#define S 5

typedef struct
{
   char pname [S];
   int ptime;
}PROCESS;

typedef struct
{
   PROCESS queue [S];
   int front;
   int rear;
}QUE;

void createQueue(QUE *);
void enCQueue(QUE *, PROCESS);
PROCESS deCQueue(QUE *);
bool isCEmpty(int,int);
bool isCFull(int,int);
void tshareProc (PROCESS);

int main(void)
{
   PROCESS p;
   QUE q;
  
   createQueue (&q);
   enCQueue (&q, p);
   tshareProc(p);
  
   return 0;
}

void createQueue(QUE *q)
{
   memset(q->queue,'\0',S);
   q->front = 0;
   q->rear = 0;
}

void enCQueue(QUE *q, PROCESS p)
{
   /*
    * Add check if queue is full.
    */
   if(q->rear == S)
   {
       printf("\n\n!! Queue is full. Cannot add more !!\n\n"); 
       return;
   }

   q->queue[q->rear] = p;
   q->rear = q->rear + 1;
}

PROCESS deCQueue(QUE *q)
{
   PROCESS p;

   /*
    * We need to properly assign the values "into" p.
    */
   p = q->queue[q->front];

   q->front = q->front + 1;

   return p;
}

bool isCEmpty(int front,int rear)
{
   if(front == S)
       return true;
   else
       return false;
}
void tshareProc (PROCESS p)
{
   QUE q;
   int i, j, x;
   bool empty, full;
   createQueue (&q);

   /*
    * Maximum "S" processes should be used.
    */
   for (i = 0; i < S; i++)
   {
  
       printf ("Enter username:");
       scanf("%s",p.pname);
       printf("Enter time in seconds:");
       scanf("%d",&p.ptime);
       while(p.ptime < 1) {
       printf("Time must be greater than zero. \nInput again:");
       scanf("%d",&p.ptime);
       }
       enCQueue (&q,p);
   }
  
   empty = isCEmpty (q.front, q.rear);
   while (!empty)
   {
       p = deCQueue (&q);

       if (p.ptime <= 10){
           printf ("\n%s's process is starting and will end in %d seconds \n", p.pname, p.ptime);

           for (j=0; j < p.ptime; j++) {

               printf("%d seconds passed\n",j+1);
               sleep(1);                             //change to sleep(1000) if giving error

           } //end of for loop
       }
       else
       {
           while(p.ptime > 0) 
           {
               printf("\n%s's process is starting and ends in %d seconds\n",p.pname, p.ptime < 10 ? p.ptime : 10);

               for(j = 0; j < (p.ptime < 10 ? p.ptime : 10); j++) {

                   printf("%d seconds passed\n",j+1);
                   sleep(1);                         //change to sleep(1000) if giving error
               } // end of for loop


               p.ptime = p.ptime - 10;
               if(p.ptime > 0)
               {
                   printf("10 seconds is subtracted in %s's process with %d seconds left\n",p.pname,p.ptime);
               }
           }
       }


       /*
        * Need to recheck the empty condition.
        */
       empty = isCEmpty (q.front, q.rear);

       //enCQueue(&q, p);
   } //end of while loop


   printf ("All processes were performed");
   return;
}