Guide to Game Development/The Programming Language/VB.NET/If Statement

Guide to Game Development/The Programming Language/VB.NET If Statement Basic math operators and Concatenation Loops If statement An 'if' statement can be used to check the value of a variable and compare it to something else. Here's a list of some comparison/conditional operators: Conditional Operator Description = Is equal to <> Is not equal to > Is greater than < Is less than >= Is greater than or equal to <= Is less than or equal to Example of an if-statement in use Dim Num1 as Integer = Console.ReadLine() If Num1 = 5 Then Console.WriteLine("They chose the number 5!") End If 'Stopping the program from closing Console.ReadLine() First run of the program Input: 5 Output: They have chose the number 5! Second run of the program Input: 4 Output: Example of a greater than being used Dim Num1 as Integer = Console.ReadLine() If Num1 > 5 Then Console.WriteLine("Their number was greater than 5!") End If 'Stopping the console from closing Console.ReadLine() First run of the program Input: 8 Output: Their number was greater than 5! Second run of the program Input: 3 Output: Third run of the program Input: 5 Output: Notice that if it was equal to 5, there was no output, to get an output for 5 as well the code could be either changed to > 4 or >= 5 Else This is to used to active when the if statement isn't true. Example of Else Statement Example code: Dim Num1 as Integer = Console.ReadLine() If Num1 >= 7 Then Console.WriteLine("Their number is greater than or equal to 7.") Else Console.WriteLine("Their number is less than 7.") End If First run of the program Input: 8 Output: Their number is greater than or equal to 7. Second run of the program Input: 7 Output: Their number is greater than or equal to 7. Third run of the program Input: 6 Output: Their number is less than 7. Else If These can be used to check for other things other than the first if statement. Example of Else If statement Dim Num1 as Integer = Console.ReadLine() If Num1 = 8 Then Console.Writeline("Equal to 8.") Else If Num1 >= 7 Then Console.WriteLine("7 and more.") Else Console.WriteLine("Everything else (6 or less).") End If 'Stopping the console from closing Console.ReadLine() First run of the program Input: 9 Output: 7 and more. Second run of the program Input: 7 Output: 7 and more. Third run of the program Input: 6 Output: Everything else (6 or less). Forth run of the program Input: 8 Output: Equal to 8. Notice that the first is accepted, but the second statement is still true, but it didn't run that piece of code, this is because with if statement it goes from top to bottom, when it finds one statement that is true, it doesn't bother checking others. A way to make both active when they're both true would be to do this: If Num1 = 8 Then Console.Writeline("Equal to 8.") End If If Num1 >= 7 Then Console.WriteLine("7 and more.") Else Console.WriteLine("Everything else (6 or less).") End If Example Input and Output for this new algorithm Input: 8 Output: Equal to 8. 7 and more. You can have many Else If statements in a row Example: Dim Num1 as Integer = Console.ReadLine() If Num1 = 5 Then Console.WriteLine("Num1 is 5") Else If Num1 = 6 Then Console.WriteLine("Num1 is 6") Else If Num1 = 7 Then Console.WriteLine("Num1 is 7") Else If Num1 = 8 Then Console.WriteLine("Num1 is 8") Else Console.WriteLine("Num1 isn't 5, 6, 7 or 8") End IF 'Stopping the console from closing Console.ReadLine() Of course this is an inefficient way of coding, a better way would be to write: Console.WriteLine("Num1 is " & Num1) However the code above doesn't allow for the else part, for this we'll need to learn about boolean logic operators as seen below. Boolean Logic Operators There are 4 main boolean logic operators available: AND, OR and XOR, NOT. Boolean logical operators compare the two boolean statements either side of it and then convert them both into another boolean statement (With the exception of NOT which only affects the boolean statement after it). They are defined as such: Operator Description Truth table And Is only true if both the statements are true, else it's false. Input to the Left Input to the right Output False False False False True False True False False True True True Or Is true if either one of the statements are true, or if they are both true. Is only false when both are false. Input to the Left Input to the right Output False False False False True True True False True True True True Xor Is true when either one are true. Is false if they are both true, or if they are both false (Only true if they are different). Input to the Left Input to the right Output False False False False True True True False True True True False Not Inverts the boolean value of the statement that follows it. Input to the right Output False True True False Example of AND Example of OR Example of XOR Example of NOT Nested If Statements 75%