c programe for hashing technique

#include<stdio.h>
#include<conio.h>
#include<stdlib.h>
int hashtable[40];
int bucket;
int hash(int key)
{
return key%100;
}
int rehash(int key)
{
return (key+1)%100;
}
void insert(void)
{
int data,count=0;
printf("enter data to insert");
scanf("%d",&data);
bucket=hash(data);
if(bucket>=40)
bucket=0;
while(hashtable[bucket]!=0)
{
bucket=rehash(bucket);
count++;
if(count>=40)
{
printf("memory full");
break;
}
}
if(hashtable[bucket]==0)
hashtable[bucket]=data;
printf("data is stored at index%d",bucket);
}
void search(void)
{
int i,isfound=0,key;
printf("enter key to search");
scanf("%d",&key);
for(i=0;i<=40;i++)
{
if(hashtable[i]==key)
{
isfound=1;
break;
}
}
if(isfound==1)
printf("found");
else
printf("not found");
}
void deleteit(void)
{
int key,i,isfound=0;
printf("enter the key to delete");
scanf("%d",&key);
for(i=0;i<40;i++)
{
if(hashtable[i]==key)
{
isfound=1;
break;
}
}
if(isfound==1)
{
hashtable[i]=0;
printf("the key is deleted");
}
else
printf("can't delete");
}
void display()
{
int i;
for(i=0;i<40;i++)
printf("%3d",hashtable[i]);
}
void main()
{
int ch,i;
for(i=0;i<40;i++)
hashtable[i]=0;
while(1)
{
printf("1.insert\n2.search\n3.delete\n4.display\nexit\n");
printf("enter your choice");
scanf("%d",&ch); {
switch(ch)
{
case 1:insert();
break;
case 2:search();
break;
case 3:deleteit();
break;
case 4:display();break;
case 5:exit(0);
default:
printf("entered choice is wrong");
}
}
}
}