Why does this give junk value?

Why does this give junk value?

I am getting garbage/junk value as output when displayed... Why is it so
can someone help me to understand how to properly pass by pointers and not
get junk value... This program is about stack creation of struct books
type variables. But by default shouldn't the variable bks pass by pointer
and change when b is changed. But bks is still storing garbage value.
Please help.
#include<stdio.h>
#include<stdlib.h>
struct books
{
int yrpub;
char name[100],author[50];
};
int top=-1;
int push(struct books b[],int top,int n)
{
if(top==n-1)
return -1;
else
{
++(top);
printf("Enter books info: \n");
printf("Enter name: ");
gets(b[top].name);
printf("Enter author: ");
gets(b[top].author);
printf("Enter Year of publish: ");
scanf("%d",&b[top].yrpub);
return top;
}
}
void display(struct books b[],int top)
{
int i;
if(top==-1)
printf("No books in the stack...");
for(i=0;i<=top;i++)
{
printf("Details of book %d: \n",i+1);
printf("Name: %s\nAuthor: %s\nYear of publish:
%d\n",b[i].name,b[i].author,b[i].yrpub);
}
system("pause");
}
int main()
{
struct books bks[10];
int ch;
system("cls");
printf("Select an option:\n");
printf("1. Push book\n2. Pop book\n3. Peep book\n4. Display all books
info\n5. Exit\n");
printf("Enter a choice: ");
scanf("%d",&ch);
fflush(stdin);
switch(ch)
{
case 1:
system("cls");
top=push(bks,top,10);
break;
case 4:
system("cls");
display(bks,top);
break;
case 5: exit(0);
default: printf("\nWrong choice...Please retry.");
long i,j;
for(i=0;i<1000000;i++)
for(j=0;j<100;j++);
}
main();
}