C menu driven program to implement 1.Binary Search 2.Linear Search techniques

#include<stdio.h>
int key;
int binary(int a[],int low,int high);
int linear(int a[],int n);
main()
{
int n,i,a[10],pos,ch;
do
{
        printf("-------Menu--------\n1.Binary Search\n2.Linear Search\n3.Exit");
printf("\nEnter your choice ");
scanf("%d",&ch);
switch(ch)
{
case 1 :
printf("\n Enter how many elements: ");
scanf("%d",&n);
printf("\n Enter elements of array\n");
for(i=0;i<n;i++)
{
scanf("%d",&a[i]);
}
printf("\n enter the elements to be searched");
scanf("%d",&key);
pos=linear(a,n);
if(pos==-1)
printf("\n element not found");
else
printf("\n element found at position %d",pos+1);
break;
case 2 :
printf("\n Enter how many elements: ");
scanf("%d",&n);
printf("\n Enter elements of array\n");
for(i=0;i<n;i++)
{
scanf("%d",&a[i]);
}
printf("\n enter the elements to be searched");
scanf("%d",&key);
pos=linear(a,n);
if(pos==-1)
printf("\n element not found");
else
printf("\n element found at position %d",pos+1);
break;

case 3 :exit(0);

default:printf("\n Invalid coice");
break;
}
}
while(ch!=3);
}
int binary(int a[],int low,int high)
{
int mid;

if(low>high)
{
return(-1);
}
mid=(low+high)/2;
if(key==a[mid])
{

return(mid);
}
if(key<a[mid])
{
return(binary(a,low,mid-1));
}
else
{
return(binary(a,mid+1,high));
}
}


int linear(int a[],int n)
{
int i;
for(i=0;i<n;i++)
{
if(a[i]==key)
return(i);
}
return(-1);
}