Difference between char* and wchar_t*

Question

I am new to MFC. I am trying to do simple mfc application and I'm getting confuse in some places. For example, SetWindowText have two api, SetWindowTextA, SetWindowTextW one api takes char * and another one accepts wchar_t *.

What is the use of char * and wchar_t *?

Answer 1

char is used for so called ANSI family of functions (typically function name ends with A), or more commonly known as using ASCII character set.

wchar_t is used for new so called Unicode (or Wide) family of functions (typically function name ends with W), which use UTF-16 character set. It is very similar to UCS-2, but not quite it. If character requires more than 2 bytes, it will be converted into 2 composite codepoints, and this can be very confusing.

If you want to convert one to another, it is not really simple task. You will need to use something like MultiByteToWideChar, which requires knowing and providing code page for input ANSI string.

Answer 2

On Windows, APIs that take char * use the current code page whereas wchar_t * APIs use UTF-16. As a result, you should always use wchar_t on Windows. A recommended way to do this is to:

// Be sure to define this BEFORE including <windows.h>
#define UNICODE 1
#include <windows.h>

When UNICODE is defined, APIs like SetWindowText will be aliased to SetWindowTextW and can therefore be used safely. Without UNICODE, SetWindowText will be aliased to SetWindowTextA and therefore cannot be used without first converting to the current code page.

However, there's no good reason to use wchar_t when you are not calling Windows APIs, since its portable functionality is not useful, and its useful functionality is not portable (wchar_t is UTF-16 only on Windows, on most other platforms it is UTF-32, what a total mess.)

Answer 3

SetWindowTextA takes char* which is a pointer to an ANSI strings and SetWindowTextW take wchar_t* can point to wide strings aka Unicode.

SetWindowText has been #defined to either of these in header Windows.h based on the type of application you are building. If you are building UNICODE build then your code will automatically use SetWindowTextW.

SetWindowTextA is there primarily to support legacy code which needs to be build as SBCS (Single byte character set)