What happens in the array when functions enqueue and dequeue are performed in the queue?

#include<stdio.h>
#define MAX4
void enquene(char*Q, charx);
char queue (char*Q);
void initialize (char*Q);
intempty (char*Q);
int head = 0;
intail = 0;
int number = 0;
void enqueue(char*Q, charx){
    if (number <MAX) {
        number++;
        tail=(tail%MAX)+1;
        Q[tail] = x;
    }
    else{
        printf("Queue Q is overflows.\n");
    }
}
char queue (char*Q) {
    if(number>0){
        number --;
        head=(head%MAX)+1;
        return(Q[head]);
    }
    else{
        printf("Queue Quality.\n");
        return('0');
    }
}
void initialize (char*Q) {
    inti;
    head = 0;
    tail = 0;
    number = 0;
    for(i=0;i<MAX;i++){
        Q[i] = '\0';
    }
}
intempty(char*Q){
    if(number==0){
        return(1);
    }
    return(0);
}
int main(void){
    charx;
    char Q [MAX];
    enqueue(Q, 'a');
    enqueue(Q, 'b');
    enqueue(Q, 'c');
    x = dequeue(Q);
    x = dequeue(Q);
    enqueue(Q, 'd');
    x = dequeue(Q);
    enqueue(Q, 'e');
    while(!empty(Q)){
        printf("%c", queue(Q));
    }
    printf("\n");
    return(0);
}