A Guide to Commands in Visual Basic
Contents
What is a Command?
A command is a specific instruction given to a computer application to perform a task or function. When referring to a programming language, a command is a unique word/keyword used to perform a specific operation.
Unlike variables, which are named and defined within your code, command names are defined by the programming language itself and cannot be changed. Differences in the names and use of different commands are essentially what make one programming language different from another.
As a programmer, you may be able to accomplish the same task coding in either Python or Visual Basic, but the code involved would be completely different between the two projects because of the way each language defines and interprets commands. Visual Basic, like any other programming language, employs commands. In this article, you are going to learn more about Visual basic commands and how to use them in your code.
Visual Basic Commands
In Visual Basic programming there is a multitude of commands and it will not be possible to list all of them in this article. Few of them will be studied here just for the purpose of understanding how they function.
Commands for String Manipulation
Asc
Function
Returns the number corresponding to the ASCII code for the first character of string
Asc(“String”)
string refers to the string containing character as first letter whose ASCII code is to be found.
Example
In this example we are going to look for the ASCII (American Standard Code Information Interchange) code of the first letter of the word “Happy” hoping that you are happy reading this article. The code will be written in an old version of a Visual Basic IDE (VB6) and a new version (VB.NET). The screenshot will be done just for this example. In the other examples we shall give only the expected outcome. Do the following:
- Create a new project in your VB IDE (VB6 or VB.NET)
- Double Click on the default form that has been created automatically in the project.
- Write the following code in the “
Form_Load
” procedure that was created when you double-clicked on the form in the previous step.
Dim code code = Asc("Happy") MsgBox "The ASCII code is " & code
Screenshot from a VB.NET IDE
Screenshot from VB6 IDE
Note: This command can be useful when you have a problem with a key on your keyboard. For example if you have a problem with letter “H” on your keyboard, knowing that the ASCII code for “H” is 72 as seen in the example above, if you type ALT + 72 on a word processor or an IDE editor, that will give you letter “H” (or Alt + 104 for “h”).
Chr
Function
Returns a string character that corresponds to the ASCII code in the range 0-255. It is the reverse of the Asc function.
Syntax
Chr(code)
code = ASCII code.
Example
char = Chr(72)
Here char gets value “H”
Read the full tutorial about Chr here.
Len
Function
Returns the length of a given string or 0 for Empty.
Syntax
Len(expression)
expression = a string
Example
Mystring = InputBox("Enter a string to get the length")
length = Len(Mystring)
MsgBox "The length of the string is " & length
e.g. if Mystring
is “Welcome”, length will be 7.
Read the full tutorial about Len() here.
Left
Function
Returns a given number of characters from the left-hand side of a string
Syntax
Left(string,x)
string = string to use
x = number of characters
Example
mystring = InputBox("Enter a string")
mystring = Left(mystring, 5)
MsgBox "First five characters of your input are " + mystring
e.g. where the input mystring
is “Welcome”, the output mystring will be “Welco”
Right
Function
Returns a given number of characters from the right-hand side of a string
Syntax
Right(string, x)
string = string to use
x = number of characters
Example
mystring = InputBox("Enter a string")
mystring = Right(mystring, 4)
MsgBox "Last four characters of your input are " + mystring
e.g. where the input mystring
is “Welcome”, the output mystring will be “come”
For more info about substring functions, see our article here.
Trim
Function
Removes leading and trailing spaces from a string
Syntax
Trim(string)
string = string to use
Example
mystring = Trim(mystring)
e.g. where the original value of mystring was ” Hello “, the new value of mystring will be “Hello”.
When using Trim, make sure you don’t run into common errors that may come up.
LCase
Function
Converts a string to lowercase (while Ucase converts a string to uppercase)
Syntax
Lcase(string)
string = string to use
Example
mystring = LCase(mystring)
e.g. where the original value of mystring
was “HELLO”, the new value of mystring will be “hello”.
String
Function
Creates a string with the specified length of the specified character
Syntax
String(length, character)
length = length of string
character = character to fill string with
Example
mystring = String(5,"a")
e.g. the new value of mystring will be “aaaaa”.
Mathematical Functions
Abs
Function
Returns the absolute value of a number
Syntax
Abs(number)
Example
msgbox "The absolute value of -4 is " & abs(-4)
Note: The Abs function only accepts numbers. Non-numeric values generate an error.
Int
Returns the integer portion of a number.
Int(n)
Where n is the number to return
Example
Int(10)
Returns 10
Int(5.1)
Returns 5
Input and Output Commands
MsgBox
Function
The MsgBox function displays a message in a dialog box, waits for the user to click a button, and returns an Integer value indicating which button the user clicked.
Syntax
MsgBox(prompt[, buttons] [, title] [, helpfile, context])
Examples
MsgBox "An error has occurred!",vbExclamation,"Error"
Response=MsgBox("Yes or no?",vbYesNo + vbQuestion,"Choose one")
InputBox
Function
Displays a simple input box for user to enter data
Syntax
Variable=InputBox(Prompt,Title)
Variable = variable to which the input value will be stored Prompt = text displayed to the user in the input box Title = title of the input box
Examples
myint=InputBox("Enter a number","Enter a number")
Date and Time
Date
Function
Returns or sets the current system date
Example
MsgBox "Today 's date is " & Date & "."
Time
Function
Returns or sets the current system time
Example
MsgBox "The time now is " & Time & "."
Timer
Function
Returns the number of seconds since midnight
Example
NumHrs=Int(Timer / 3600)
MsgBox "Currently in hour " & NumHrs
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