Using numbers for calculations in Visual Studio .NET

Drawer UPCA in Visual Studio .NET Using numbers for calculations

Numbers form the basis for a lot of the information computers store You use numbers to perform tasks in a spreadsheet, to express quantities in a database, and to show the current page in a document Programs also use numbers to count loops, to determine the position of characters in a string, and to check the truth value of a statement And VBA uses numbers to determine which character to display on-screen or how to interact with your code

You look at a number as a single entity a number is simply a number The computer views numbers in several different ways because the processor

actually works with different kinds of numbers in different ways ( In fact, at one time, the math coprocessor used to work with money and numbers with decimal points with separate chips within the computer) The four basic number types include Integer: This is a number without a decimal An integer can hold any whole number, such as 5, but not a number with a decimal, such as 50 Although these two numbers are the same, the first is an integer, and the second isn t Real: A real number is (for all practical purposes) one that contains a decimal point The decimal portion doesn t have to contain a value The number 50 is a perfectly acceptable real number A real number is stored in a completely different format than an integer (The storage technique only matters to the processor you don t need to know it to use VBA) Currency: Financial calculations usually require special accuracy Even a small error can cause problems The Currency numeric type stores numbers with extreme precision, but at an equally large cost in both processing time and memory use Decimal: Computers normally store information by using a base-2 ( binary) format You use a base-10 (decimal) format for working with numbers Small errors can occur when converting from one numbering system to the other and these can accumulate into huge errors The decimal numeric system stores numbers in a simulated base-10 format, which eliminates many computing errors However, this system requires more memory and processing time than any other numeric type Computers also determine a numeric type based on the amount of memory that the data requires VBA supports three integer types, including Byte (1 byte of storage), Integer (2 bytes of storage), and Long (4 bytes of storage) The extra memory stores larger numbers: 0 to 255 for Byte; 32,768 to 32,767 for Integer; and 2,147,483,648 to 2,147,483,647 for Long Listing 3-4 demonstrates various data types

Public Sub DataRange() Declare the numeric variables Dim MyInt As Integer Dim MySgl As Single Dim MyDbl As Double Dim MyCur As Currency Dim MyDec As Variant

Define values for each variable MyInt = 30 + 000010001000111 MySgl = 30 + 000010001000111 MyDbl = 30 + 000010001000111 MyCur = 30 + 000010001000111 MyDec = CDec(30 + 000010001000111)

Display the actual content MsgBox Integer: + TwoTab + CStr(MyInt) + _ vbCrLf + Single: + TwoTab + CStr(MySgl) + _ vbCrLf + Double: + TwoTab + CStr(MyDbl) + _ vbCrLf + Currency: + vbTab + CStr(MyCur) + _ vbCrLf + Decimal: + TwoTab + CStr(MyDec), _ vbOKOnly, _ VBA Data Types End Sub

The first few variable types use standard declarations However, notice that you can t declare the decimal data type directly you must declare it as a Variant in VBA (See the Working with variant data section for more information about the Variant type) The code assigns each variable the same value Notice that the code must use the CDec function to insert a decimal value into the Variant because VBA doesn t include a decimal data type The application output demonstrates something interesting about the numeric data types Each type silently dropped any decimal data it couldn t hold This is just one of many reasons to carefully consider the numeric data type you use