Data Type Characters

Also known as Data Type Suffixes, Type Declaration Characters or Variable Declaration Characters.
This is not used so much know but does work and it saves space.
It is also possible to tell VBA the type of a variable by appending a special character to the end of the variable name.

Dim sFirstName$     'String  
Dim iNumber%        'Integer  
Dim lAverage&       'Long  
Dim sngTotal!       'Single  
Dim dbTotal#        'Double  
Dim cProfit@        'Currency  
Dim llDiscount^     'LongLong on 64 bit  

Type Declaration Characters

VBA does allow you to append a character to a variable's name as a quick way of indicating its data type.
This method of declaring variables should not be used and is only available for backwards compatibility purposes.
The following line will declare a variable with a Double data type

Dim dbDouble# 

This line however should be declared using the "As" keyword.

Dim dbDouble As Double 

Variable Declaration Characters

When you declare a literal constant or when you are performing a calculation you may want a specific data type to be used.
When you use the Variant data type the compiler is able to determine the correct data type for a numerical literal.
However there might be times when the default data type is different to the desired one.

Dim myVariant1 As Variant 
Dim myVariant2 As Variant 
myVariant1 = 100 
myVariant2 = 100# 

Debug.Print VBA.TypeName(myVariant1)  'Integer   
Debug.Print VBA.TypeName(myVariant2)  'Double   

Example

Dim myDouble As Double 
Dim myInteger As Integer 

myInteger = 32767 
myDouble = myInteger * 100      ' the result is an Integer since both operands are Integer  
Debug.Print myDouble            ' error overflow  

myDouble = myInteger * 100#     ' tells it that 100 is a Double  
Debug.Print myDouble            ' 3276700