Hey i have created binary search prograram
this progaram search all locations but not first
if i give value of other than zero location it gives results
but not for zero location
please guid me
the code is as follows

// Program for Binary search
#include<stdio.h>
#include<conio.h>
int a[50];
void main()
{
	int ch1=0,n=0,i;
	clrscr();
	while(ch1!=4)
	{
		printf("\n 1 : Read data ");
		printf("\n 2 : Search data ");
		printf("\n 3 : Show data ");
		printf("\n 4 : Exit ..... ");
		printf("\n Enter your choice: ");
		scanf("%d",&ch1);
		switch(ch1)
		{
			case 1:
				printf("\n Enter no of values to read : ");
				scanf("%d",&n);
				for(i=0;i<n;i++)
				scanf("%d",&a[i]);
				break;
			case 2:
				printf("\n Enter valu to be search : ");
				scanf("%d",&i);
				i=bsearch(a,0,n-1,i);
				if(i>0)
				printf("\n Value is found at index %d ",i);
				else
				printf("\n Value is not found ");
				  break;
			case 3:
				for(i=0;i<n;i++)
				printf("\n %5d",a[i]);
				break;

		}
	}
}

int bsearch(int a[],int lb,int ub,int target)
{
	int mid;
	if(lb<=ub)
	{
		mid=(lb+ub)/2;
		if(a[mid]==target)
		return mid;
		else if(a[mid]>target)
		bsearch(a,lb,mid-1,target);
		else
		bsearch(a,mid+1,ub,target);

	}
	else
	 return -1;

}

At first sight there seems to be nothing wrong with your search.
Is your input sorted? This is rather essential.

Your Binary Search Function's logic is right but You have some simple errors :-
Firstly in the function since u intending using Recursion then u have to return the value that is resulted from the backtracking to a Variable and return this Variable to the Main function.

int bsearch(int a[],int lb,int ub,int target)
{
    int result; //Here is the variable that accepts the result of the backtracking
	int mid;
	if(lb<=ub)
	{
		mid=(lb+ub)/2;
		if(a[mid]==target)
		return mid;
		else if(a[mid]>target)
		result=bsearch(a,lb,mid-1,target);
		else
		result=bsearch(a,mid+1,ub,target);

	}
	else
	 return -1;

     return result;
}

Secondly:-
In the main function in case '2' when the function returns the index of the first value of the array to variable i the index that will be returned is 0
and since u made a check if i>0 only it will print "Value is not found"
here is the correction

case 2:
{
	printf("\n Enter valu to be search : ");
	scanf("%d",&i);
	i=bsearch(a,0,n-1,i);
	if(i>=0) //Here is the correction just add the "=" sign
	printf("\n Value is found at index %d ",i);
	else
	printf("\n Value is not found ");
	break;
}

Thirdly:-
MAKE SURE that the values stored in the array is SORTED .


I'll be happy of Any critique .

result=bsearch(a,lb,mid-1,target);

Quite right Ahmed_l, I overlooked it! But it is easier to say : return bsearch(a,lb,mid-1,target); that way you don't need the extra result variable.

Quite right Ahmed_l, I overlooked it! But it is easier to say : return bsearch(a,lb,mid-1,target); that way you don't need the extra result variable.

Mr ddanbe,
It is only matter of style not more and this is a small program so it doesn't matter if i added another variable, ofcourse u right and thanks for this advice.

this is a small program so it doesn't matter

I was not making any criticism here. If you want to use a variable, please do. Nobody will get hurt.
But in programming you must always be aware of optimisation, so if you can, do it.

hey u have not solve my problem
do u undetstand my problem
its not givinig 1 st locatotion value
when search for frist location

Excuse me, But could you plz explain your problem more efficiently.
cuz i didn't get your point

If you are searching for the number 3(target) and if a[0) contains 3 you will get the index which is 0 you will not get the value which is 3, but that was the value you where searching in the array a. So 0 means you found the value 3 in the array, otherwise if the value 3 was not in your array you would have gotten the value -1.