Differences in String Function Operations

Office 2010

The memory storage formats for text differ between Visual Basic for Applications (VBA) code and Access Basic code. (Access Basic was used in early versions of Microsoft Access.) Text is stored in ANSI format within Access Basic code and in Unicode format in Visual Basic.

The Unicode format is used in Visual Basic to match the format of text within OLE, which is indirectly related to Visual Basic.

For example, the text string "ABCfe140_ZA06051646fe086_ZA06051620fe228_ZA06051709" would be stored in memory as shown below.

Storage format

Storage pattern

Description

Unicode

41 00 42 00 43 00 42 30 44 30 46 30

Each character is stored as 2 bytes.

ANSI

41 42 43 82 A0 82 A2 82 A4

ASCII characters are stored as 1 byte; double-byte characters are stored as 2 bytes.

Because of these differences in internal format, there are string processing functions that operate differently in Access Basic and Visual Basic. The functions that operate differently and their statements are as shown below.

Asc function, Chr function, InputB function, InStrB function, LeftB function, LenB function, RightB function, MidB function, and their corresponding statements.

Also, the ChrB function and AscB function have been added to Visual Basic.

In that these functions and statements both process text in byte units, they are the same in Access Basic and Visual Basic, but because their storage formats for text are different, they operate differently. For example, LenB("A") would be 1 in Access Basic, but 2 in Visual Basic.

Programs created in previous versions of Microsoft Access that use the string processing functions that work in byte units must be changed in Visual Basic to a source code that recognizes Unicode. However, if only string processing functions that process character units, such as the Len function, Left function, and Right function, are used, there is no need to recognize them.

If programs created in a previous version of Microsoft Access are moved to the current version of Microsoft Access, consider issues discussed in the following topics regarding string processing.

Asc Function and AscB Function

Chr Function and ChrB Function

Calling the Windows API

Input and InputB Functions

Processing ANSI String Bytes

Sample Functions that perform operations that are compatible with byte processing functions of 16-bit versions

Using the Byte Data Type

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