My requirement is to add two binary numbers, say "1001" and "0101" as binary1 and binary2.

Partial Class Default2
Inherits System.Web.UI.Page
Dim carry As Boolean = False ' Boolean variable to hold the carry if occured
Protected Sub Button1_Click(sender As Object, e As System.EventArgs) Handles Button1.Click
Dim binary1 As String = TextBox1.Text 'First binary number
Dim binary2 As String = TextBox2.Text 'Second binary number
Dim result As String = "" 'to store the result
For i As Integer = Len(binary1 ) - 1 To 0 Step -1
result = bin_add(getbyte(binary1 , i), getbyte(binary1, i)) & result ' calling function
Next
If carry = True Then
result = "1" & result 'if a carry remains add it to the MSB
End If
MsgBox(rslt) 'Display the result
End Sub

Public Function bin_add(b1 As Boolean, b2 As Boolean) As String'Function which performs the addition of each single bits form the two inputs which is passed from the calling function
Dim result As Boolean
If b1 AndAlso b2 = True Then 'both values are 1/true
If carry = True Then
result = True
carry = True
Else
result = False
carry = True
End If
ElseIf b1 = False And b2 = False Then 'Both are 0/false
If carry = True Then
result = carry
carry = False
Else
result = False
carry = False
End If
Else
If carry = True Then
result = False
carry = True
Else
result = True
carry = False
End If
End If
If result = True Then
Return "1" 'return 1 for Boolean true
Else
Return "0" 'return 0 for Boolean false
End If
End Function

Private Function getbyte(s As String, ByVal place As Integer) As String'Function for getting each individual letters from the input string. i got it from net.
If place < Len(s) Then
place = place + 1
getbyte = Mid(s, place, 1)
Else
getbyte = ""
End If
End Function
End Class


Notes:

• It gives good results for me only if the no. of digits in both numbers are the same.

Question:

How can I improve the code? Especially, how can I reduce the length of code?

• We don't accept broken code, so I would stick to the first question. But just really quick: prepend the shorter input with enough 0s so that it has the same length (I'm assuming only positive numbers here) – tim Aug 18 '14 at 9:49
• In addition to @tim, you can use String.PadLeft() to fill the shorter input. Also check the display of the result. If you have this included in your question, we will help you to do the same only cleaner. – Heslacher Aug 18 '14 at 10:13
• I'll refrain from a review, but are you aware that the And Keyword does bitwise addition? Once the binary representation is converted to an integer, this should be trivial. – RubberDuck Aug 18 '14 at 10:26
• while evaluating this i got correct answer. i need to shorten the code, and make it workable with all inputs – Little Master Aug 18 '14 at 10:28
• @LOsunG make it workable with all inputs -> that's asking others to implement functionality for you, Therefore it is beyond the scope of code review. i need to shorten the code -> This is OK ,because code review is to improve the code.Even though shortening is not always better. – bhathiya-perera Aug 18 '14 at 13:45

For now, let's ignore the fact that there are easier ways to add binary numbers. There are other issues with this code.

Inherits System.Web.UI.Page


Why is code that adds binary numbers inheriting from a UI class? There's no need for this. Separate the concerns and create a module for this code instead.

carry is scoped to the class level. This is a symptom of problems in this code.

Protected Sub Button1_Click(sender As Object, e As System.EventArgs) Handles Button1.Click
Dim binary1 As String = TextBox1.Text 'First binary number
Dim binary2 As String = TextBox2.Text 'Second binary number
Dim result As String = "" 'to store the result
For i As Integer = Len(binary1 ) - 1 To 0 Step -1
result = bin_add(getbyte(binary1 , i), getbyte(binary1, i)) & result ' calling function
Next
If carry = True Then
result = "1" & result 'if a carry remains add it to the MSB
End If
MsgBox(rslt) 'Display the result
End Sub


Getting the values from the UI makes sense, but then you loop over bin_add, which obviously doesn't actually add anything, or you wouldn't need to loop or have a class variable. All of this logic should happen inside of bin_add.

bin_add should take in two strings, handle all of the logic, and return a single string representing the output. While I'm at it, methods should have PascalCased verb-noun names. This method should be called AddBinary and I will refer to it as such for the rest of the review.

As I said earlier, I wouldn't expect a Function that adds binary numbers to take in Boolean values. I would rather it actually take in a byte and overload the method to handle string representation, but I'm lazy and you don't seem to need all that.

Putting it all together, the signature line

Public Function bin_add(b1 As Boolean, b2 As Boolean) As String


Should look like this.

Public Function AddBinary(value1 as String, value2 as String) As String


Implementing this change will be left as an exercise for the reader.

Once the user input is validated to be ones or zeros in the textboxes the conversion / addition is simple. Using the OP's input parameters:

    'verify user input as a binary digit
For Each c As Char In TextBox1.Text
If Not (c = "0"c OrElse c = "1"c) Then
Stop 'not a binary digit - error handling needed
Exit Sub
End If
Next

For Each c As Char In TextBox2.Text
If Not (c = "0"c OrElse c = "1"c) Then
Stop 'not a binary digit - error handling needed
Exit Sub
End If
Next

'http://msdn.microsoft.com/en-us/library/1k20k614%28v=vs.110%29.aspx
Dim num1 As Integer = Convert.ToInt32(TextBox1.Text, 2)
Dim num2 As Integer = Convert.ToInt32(TextBox2.Text, 2)

Dim answer As Integer = num1 + num2


One of the overloads to Convert.ToInt32 accepts a base(radix) to be used in the conversion.

• You might want to add, which (by the way absolutely cool) feature of .net you're exploiting, including a link to documentation ;) Additionally you could make the code easier to understand by extracting TextBox1.Text and TextBox2.Text to local variables, but that's yours to decide – Vogel612 Aug 18 '14 at 11:35