This message is posted to the window with the keyboard focus when a WM_KEYDOWN message is translated by the TranslateMessage function. WM_CHAR contains the character code of the key that was pressed.
WM_CHAR chCharCode = (TCHAR) wParam; lKeyData = lParam;
Specifies the character code of the key.
Specifies the repeat count, context code, previous key-state flag, and transition-state flag, as shown in the following table.
Specifies the repeat count. The value is the number of times the keystroke is repeated as a result of the user holding down the key.
Specifies the context code. The value is 1 if the ALT key is held down while the key is pressed; otherwise, the value is 0.
Specifies the previous key state. The value is 1 if the key is down before the message is sent, or it is 0 if the key is up.
Specifies the transition state. The value is 1 if the key is being released, or it is 0 if the key is being pressed.
Because there is not necessarily a one-to-one correspondence between keys pressed and character messages generated, the information in the high-order word of the lKeyData parameter is generally not useful to applications. The information in the high-order word applies only to the most recent WM_KEYDOWN message that precedes the posting of the WM_CHAR message.
Keys that do not produce printable characters, such as any of the VK_F* keys, must never generate a WM_CHAR message.
For enhanced 101- and 102-key keyboards, extended keys are the right ALT and the right CTRL keys on the main section of the keyboard; the INS, DEL, HOME, END, PAGE UP, PAGE DOWN and arrow keys in the clusters to the left of the numeric keypad; and the divide (/) and ENTER keys in the numeric keypad. Some other keyboards may support the extended-key bit in the lKeyData parameter.