Whether or not characters can combine depends on the keyboard mode. WinVNKey currently supports five modes:
WinVNKey is inactive as if it were never running.
You can turn off WinVNKey via the user interface
or by clicking on the VN icon on the taskbar tray. When
WinVNKey is off, the taskbar tray icon turns into a STOP sign 
. If
you click again, it will change to AutoCombine mode and the the icon becomes
.
.
In this mode every character you type in will automatically combine with the previous character into Vietnamese if possible. This mode is recommended if you are typing mostly Vietnamese text. For instance, ma' to^i ==> má tôi
In this mode characters do not combine unless you request explicitly by preceding the base letter with an escape character. For instance, Hello Kh\o^i ==> Hello Khôi. This mode is recommended if you are typing mostly English text with some Vietnamese words occasionally . Smart Viet options are not available in this mode; accent marks must be typed immediately after the base letters.
In this mode what you type is what you get except perhaps these special sequences: \V, \M, \L, \S, \v, \m, \l. These sequences allow fast mode switching and can be enabled or disabled in the Advanced page.
In this mode WinVNKey sleeps and hence does not combine characters. Basically, what you type is what you get except the wake-up sequence, defined by default as \WK! (exactly four characters \ W K and ! ). When you type \WK!, WinVNKey will wake up and generate 4 backspaces to erase \WK!. The new mode will be the same mode that WinVNKey was in before the sleep. The sleep mode is as good as OFF mode for use in typing characters without accent marks to avoid unwanted combination. The advantage is that it allows fast mode switching simply by typing so that the user does not have to move his fingers off the keyboard.
Note that for keyboarding purposes it is sufficient to support only one mode (mode 1) because the user can use hot keys to turn on/off Vietnamese mode. However, the purpose of WinVNKey is to support the VIQR standards, which were designed to handle Vietnamese data in keyboard entry and in input/output streams (e.g. text files, where hot keys are impossible). Thus WinVNKey decides to support all VIQR modes including the sleep mode extension first introduced in MacVNKey.