Dequeue using array and stucture

#include<stdio.h>
#define MAX 10
struct queue {
    int r,f,data[MAX];
}q;
int empty() {
    if(q.r==-1) return (1);
    return (0);
}
int full() {
    if((q.r+1)%MAX==q.f) return (1);
    return (0);
}
void enqueueR(int x) {
    if(q.r==-1) {
        q.r=q.f=0;
        q.data[q.r]=x;
    }
    else {
    q.r=(q.r+1)%MAX;
    q.data[q.r]=x;
    }
}
void enqueueF(int x) {
    if(q.r==-1) {
        q.r=q.f=0;
        q.data[q.f]=x;
    }
    else {
    q.f=(q.f-1+MAX)%MAX;
    q.data[q.f]=x;
    }
}
int dequeueF() {
    int x;
    x=q.data[q.f];
    if(q.r==q.f) {
        q.r=-1;
        q.f=-1;
    }
    else
        q.f=(q.f+1)%MAX;
    return x;
}
int dequeueR() {
    int x;
    x=q.data[q.r];
    if(q.r==q.f) {
        q.r=-1;
        q.f=-1;
    }
    else
        q.r=(q.r-1+MAX)%MAX;
    return x;
}
void print() {
    int i;
    if(!empty()) {
        printf("\n");
        for(i=q.f;i!=q.r;i=(i+1)%MAX)
            printf("%d\t",q.data[i]);
        printf("%d\t",q.data[i]);
    }
}
void main() {
    q.r=-1;
    q.f=-1;
    int n,x;
    do {
        printf("\n1: INSERT FRONT\n2: INSERT REAR\n3: DELETE FRONT\n4: DELETE REAR\n5: PRINT ELEMENTS\n6: QUIT");
        printf("\nENTER YOUR CHOICE");
        scanf("%d",&n);
        switch(n) {
            case 1: printf("\n ENTER A VALUE");
            scanf("%d",&x);
            if(!full())
            enqueueF(x);
            else
            printf("\nQUEUE IS FULL");
            break;
            case 2: printf("\n ENTER A VALUE :");
            scanf("%d",&x);
            if(!full())
            enqueueR(x);
            else
            printf("\n QUEUE IS FULL");
            break;
            case 3: if(!empty()) {
            x=dequeueF();
            printf("\nDELETED DATA =%d",x);
            }
            else printf("\n QUEUE IS EMPTY !!");
            break;
            case 4: if(!empty()) {
            x=dequeueR();
            printf("\nDELETED DATA =%d",x);
            }
            else printf("\n QUEUE IS EMPTY !!");
            break;
            case 5: print(); break;
            case 6: exit(0);
        }
    }while(1);
}