This depends on the content stored in the byte array. Because the function expects a NULL terminated string, the byte array must contain such a string. You must also know the text encoding for the stored string. Assuming your byte array contains an ASCII or ANSI string, you can call _strlwr: _strlwr((char *)byteArray); The casting to char * avoids compiler warnings or errors because BYTE is unsigned (unsigned char). If the resulting string must be printed out later with Unicode builds, convert it using the MultiByteToWideChar function (Windows)[^]. If it is ASCII or uses the current code page of the user running the application, it can be also converting by assigning the lowered string to a CString: CString strLwr = _strlwr((char *)byteArray); The above will work for Unicode and multi byte builds (with Unicode builds, the string is converted to Unicode).

std::find is a function to search for an identical value of a specific type. If you have different types it won't work. This includes arrays of same type but different length. What you are probably looking for is some kind of 'contains' (like strstr) or 'begins with' (like memcmp and strncmp with length of searching value) function which you have to implement yourself. Example: for (int i = 0; i < m_vec.size(); i++) { if (MySearch(m_vec.at(i), searchValue)) { // found break; } }