Array of structures lose data while passing it in C - arrays

Question

I don't understand why printq() function prints 0, but when I access it back in main() it prints. I don't understand what I am doing wrong, I tried using pointers, but I get some different error in the priority queue. I want to print elements in array pq[10].
EDIT: I realized that the elements are stored but when I use pq[R].data it prints
but when I use pq[i].data in printq() and put it inside for loop, it prints zero.
#include <stdio.h>
int F = -1, R = -1;
int item, max = 10;
struct prioq {
int data;
int prio;
};
struct prioq pq[10] = { 0 };
void printq()
{
int i = 0;
printf("%d,", pq[i].data);
printf("QUEUE :");
for (i = 0; i < max; i++) {
printf("%d,", pq[i].data);
}
printf("\n");
printf("PRIO :");
for (i = 0; i < max; i++) {
printf("%d,", pq[i].prio);
}
}
void enqueue(int item, int p, struct prioq pq[])
{
if (F == -1 && R == -1 || F > R) {
F == 0;
R == 0;
pq[R].data = item;
pq[R].prio = p;
printf("%d", pq[R].data);
printf("%d", pq[R].prio);
printq();
} else if (R == max-1 || R > max) {
printf("overflow\n");
} else if (R < max) {
R++;
pq[R].data = item;
pq[R].prio = p;
printq();
}
}
void dequeue(struct prioq pq[])
{
int large = 0;
if (F == -1) {
printf("underflow\n");
} else {
int i;
for (i = 0; i < max; i++) {
if (pq[i].prio > large) {
large = i;
}
}
}
item = pq[large].data;
pq[large].prio = 0;
pq[large].data = 0;
printf("item deleted: %d\n", item);
printq();
}
void main()
{
int item = 0;
int c = 0, p = 0;
do {
printf("choose your option\n");
printf("1.Insert, 2.Delete, 3.Exit\n" );
scanf("%d", &c);
switch (c) {
case 1:
printf("Enter the priority and element to insert\n");
scanf("%d %d", &item, &p);
enqueue(item,p,pq);
printf("%d", pq[R].data);
printf("%d", pq[R].prio);
break;
case 2:
dequeue(pq);
break;
default:
c = 3;
break;
}
} while (c != 3);
printf("exited\n");
}

Answer 1

In your enqueue function, change the == in the F and R assignments to =.
void enqueue(int item, int p, struct prioq pq[])
{
if (F == -1 && R == -1 || F > R) {
F = 0; // Here
R = 0; // And here
pq[R].data = item;
pq[R].prio = p;
printf("%d", pq[R].data);
printf("%d", pq[R].prio);
printq();
} else if (R == max-1 || R > max) {
printf("overflow\n");
} else if (R < max) {
R++;
pq[R].data = item;
pq[R].prio = p;
printq();
}
}