The high-level string format (HLSTR) used by VB3 Just for comparison (and to show that we are more fortunate now), Figure 6-1 shows the format for the VB string data type under Visual Basic 3, called an HLSTR ( High-Level String). Underwent a radical change between versions 3 and 4 of Visual Basic, due in part to an effort to make the type more compatible with the Win32 operating system. We had better elaborate on this.Īctually, the VB string data type defined by: A BSTR is, in fact, a pointer to a null-terminated Unicode character array that is preceeded by a 4-byte length field.
We are defining a member of a data type called BSTR, which is short for Basic String. We are not defining a Unicode character array per se. Here is the key to understanding strings: when we write the code: To avoid any possibility of ambiguity, we will refer to this type of object as a Unicode character array which is, after all, precisely what it is! This also helps distinguish it from an ANSI character array, that is, an array of characters represented using single-byte ANSI character codes. This is fine, but it is definitely not how we should think of strings in VB programming. Note, however, that because words are written with their bytes reversed in memory, the string "help" appears in memory as: Thus, the string ''help" is represented as: For instance, the ASCII representation for the character h is &H68, so the Unicode representation is &H0068, appearing in memory as 68 00. Put another way, VB uses Unicode to represent the characters in a string. For Visual Basic, all characters are represented by 2-byte Unicode integers. It seems to me that Microsoft is trying to say that the underlying set for the String data type is the set of finite-length sequences of characters. Just what is a string in Visual Basic? According to the VB documentation, it is:Ī data type consisting of a sequence of contiguous characters that represent the characters themselves rather than their numeric values.
The main problem is that the term string is used in at least two different ways in Visual Basic! The subject of strings can be quite confusing, but this confusion tends to disappear with some careful attention to detail (as is usually the case).
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