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Visual Basic 2010 (Console) Guide
Logical Bitwise Operators
Bitwise operators are used when we want to manipulate the individual bits in a bit pattern. You need to understand binary to follow this. There are 4 main operations,
- NOT
- AND
- OR
- XOR
The effect of these operations is shown in the truth tables below.
The NOT Gate
Takes only one input and returns the opposite. Sometimes this gate is referred to as an inverter.
| Input A | Output |
| 0 | 1 |
| 1 | 0 |
The AND Gate
Takes two inputs, the output is true if both inputs are true.
| Input A | Input B | Output |
| 0 | 0 | 0 |
| 0 | 1 | 0 |
| 1 | 0 | 0 |
| 1 | 1 | 1 |
The OR Gate
Takes two inputs, the output is true if either of the inputs is true.
| Input A | Input B | Output |
| 0 | 0 | 0 |
| 0 | 1 | 1 |
| 1 | 0 | 1 |
| 1 | 1 | 1 |
The XOR/EOR Gate
The exclusive or gate takes two inputs. The output is true if one input is true but not both.
| Input A | Input B | Output |
| 0 | 0 | 0 |
| 0 | 1 | 1 |
| 1 | 0 | 1 |
| 1 | 1 | 0 |
Getting All Logical In Visual Basic - NOT
The following program performs a NOT operation on an integer variable.
Dim a As Integer = 13
Dim b As Integer
b = Not a
Console.WriteLine(b)
Console.ReadLine()
The output you get from this program is -14. Let's see if that's what we should be expecting. We started with a value for a of 13. In binary this is,
00001101
If we invert each of these bits, we get the following,
11110010
In denary, this value is -128 + 64 + 32 + 16 + 2 = -14.
Getting All Logical In Visual Basic - AND
The following program performs a AND operation on the integer variables a and b.
Dim a As Integer = 13
Dim b As Integer = 17
Dim c As Integer
c = a And b
Console.WriteLine(c)
Console.ReadLine()
The output you get from this program is 1. Is that right? The values for a and b are 13 and 17 respectively. In binary this is,
00001101
00010001
The AND operation returns a bit only where the bits from both numbers are set to 1. The only bit this happens for is for the unit bit. The answer is therefore 1.
Getting All Logical In Visual Basic - OR
The following program performs a OR operation on the integer variables a and b.
Dim a As Integer = 13
Dim b As Integer = 17
Dim c As Integer
c = a Or b
Console.WriteLine(c)
Console.ReadLine()
The output from this program is 29. Is that what we expect? The values for a and b are 13 and 17 respectively. In binary this is,
00001101
00010001
The OR operation returns a bit if either or both of the bits are set to 1. In this case, this gives the new binary number,
00011101
This is equal to 16 + 8 + 4 + 1 = 29
Getting All Logical In Visual Basic - XOR
The following program performs a XOR operation on the integer variables a and b.
Dim a As Integer = 13
Dim b As Integer = 17
Dim c As Integer
c = a Xor b
Console.WriteLine(c)
Console.ReadLine()
The output from this program is 28. Is that what we expect? The values for a and b are 13 and 17 respectively. In binary this is,
00001101
00010001
The XOR operation returns a bit if either but not both of the bits are set to 1. In this case, this gives the new binary number,
00011100
This is equal to 16 + 8 + 4 = 28
Having A Go
- Write a program that allows you to input 2 integers at the keyboard. The program should report the result of the AND, OR and XOR operations on these numbers as well as the NOT operation on each of the two numbers.
- Use your program to give you the answers to the following
- 36 AND 49
- 47 XOR 36
- 82 OR 15