Consider the following example, in which the while loop scans a string, copying all characters except 'X' into another string:

while( *sz2 )  
{  
    if( *sz2 != 'X' )  
        *sz1++ = *sz2++;  
    else  
        sz2++;  
}  

The code copies the byte at sz2 to the location pointed to by sz1, then increments sz1 to receive the next byte. But if the next character in sz2 is a double-byte character, the assignment to sz1 copies only the first byte. The following code uses a portable function to copy the character safely and another to increment sz1 and sz2 correctly:

while( *sz2 )  
{  
    if( *sz2 != 'X' )  
    {  
        _mbscpy_s( sz1, 1, sz2 );  
        sz1 = _mbsinc( sz1 );  
        sz2 = _mbsinc( sz2 );  
    }  
    else  
        sz2 = _mbsinc( sz2 );  
}  

MBCS Programming Tips
Character Comparison