Binary to 2's complement - Xtreme Visual Basic Talk

09-07-2005, 07:05 AM

girish_mu

Freshman

Join Date: Jan 2005

Location: Mauritius Island

Posts: 36

Binary to 2's complement

I would like to get a picece of coding that converts a binary value to its 2's complement. And also, how to convert the 2's complement into octal?

09-07-2005, 07:24 AM

BobThePenguin BobThePenguin is offline

Junior Contributor

Join Date: Apr 2005

Posts: 397

Quick Google Search Got Me This

OnError's Bits, Bytes and Bases Tutorial

09-07-2005, 07:47 AM

OnErr0r

Obsessive OPtimizer

Administrator
* Guru *

Join Date: Jun 2002

Location: Debug Window

Posts: 13,685

The neg instruction takes care of two's complement negation. This is simply the - operator in VB. The Oct$() function converts decimal numbers to octal base.

__________________
Quis custodiet ipsos custodues.

09-07-2005, 08:48 AM

girish_mu

Freshman

Join Date: Jan 2005

Location: Mauritius Island

Posts: 36

huh....any piece of coding available?? By the way, I don't want to use the Oct$() function...

09-07-2005, 09:08 AM

BobThePenguin BobThePenguin is offline

Junior Contributor

Join Date: Apr 2005

Posts: 397

well im not going to give you any code but a 5 second google search should get you what you need...

09-07-2005, 09:21 AM

OnErr0r

Obsessive OPtimizer

Administrator
* Guru *

Join Date: Jun 2002

Location: Debug Window

Posts: 13,685

This sounds more like a school assignment now. If you'd like to perform your own two's compliment, then first take the Not of the number then add one.

Conversion to another base requires a simple loop, the modulus operator and integer division (\).

__________________
Quis custodiet ipsos custodues.

09-09-2005, 11:12 AM

girish_mu

Freshman

Join Date: Jan 2005

Location: Mauritius Island

Posts: 36

Not operator with binary

I have the following binary: 000000000010111
When I use

Code:

Not(000000000010111)

, it is automatically reduced to Not (10111) and the result obtained is -10112 .
How do I get 1111111111101000 ???

09-09-2005, 11:27 AM

GavinO

Coder of Fortune

Retired Leader
* Expert *

Join Date: Dec 2002

Location: Troy, NY USA

Posts: 3,120

VB is interpreting that number as an integer literal in base 10, if that is the actual code that you're running. VB doesn't have a facility for base 2 integer literals. There are various snippets about for interpreting strings in this way, but doing that at runtime is rather costly. Better would be to work out your base 2 literals in base 16, which VB does support with the &H prefix. Additionally, if you want a literal to be interpreted as a Long (32-bit) when it is small enough to be an Integer (16-bit), you need to suffix the literal with &. For example, 11111111 as a 32-bit integer:

&HFF&

__________________
-- The Gavster
Like to IRC? Try irc.randomirc.com
GavServer

09-09-2005, 11:32 AM

Val

Senior Contributor

Join Date: May 2003

Location: Vancouver, WA

Posts: 1,268

If I understood you correctly -

You are trying to invert a binary number by directly entering it into Visual Basic. As far as I know, Visual Basic does not understand binary numbers. If you want to do something of that sort, you use C++.

In other words, when you enter 000000000010111, Visual Basic interprets it as a decimal number 10111, ignoring all the zeroes up front. The inverse of 10111 is -10112, which is absolutely correct. The bottom line is - it is impossible to directly enter a binary number into Visual Basic. You either have to use another language, or a workaround.

One possibly workaround is to treat a binary number as a string, and add conversion functions to convert the binary number to and from bytes. All the operations, though, will work directly on a string. This will be horribly slow, but it will work.

For example, a Not function on a binary number expressed as a string:

Code:

Function SB_NOT(ByVal binum As String) As String
Dim biret As String
Dim i As Integer
Dim iLen As Integer

    iLen = Len(binum)

    For i = 1 To iLen
        biret = biret & IIf(Mid$(binum, i, 1) = "1", "0", "1")
    Next

    SB_NOT = biret
End Function

#10

09-09-2005, 11:40 AM

girish_mu

Freshman

Join Date: Jan 2005

Location: Mauritius Island

Posts: 36

Thank You (both of u)!!

#11

09-09-2005, 11:44 AM

OnErr0r

Obsessive OPtimizer

Administrator
* Guru *

Join Date: Jun 2002

Location: Debug Window

Posts: 13,685

I suggest you operate on longs and then convert to binary or hex, much like Gavin mentioned. If you've read my tutorial linked in the second post of this thread, then you should understand the relationship between binary and hex.

Code:

Public Function NotNumber(Byval lIn As Long) As Long
  NotNumber = Not(lIn)
End Function

From there make a string function to convert from a long to binary (string), or just use Hex$.

__________________
Quis custodiet ipsos custodues.

Last edited by OnErr0r; 09-09-2005 at 11:51 AM.