Character Constants

The Interface Kit defines constants for characters that aren’t normally represented by a visible symbol. This includes the usual space and backspace characters, but most invisible characters are produced by the function keys and the navigation keys located between the main keyboard and the numeric keypad. The character values associated with these keys are more or less arbitrary, so you should always use the constant in your code rather than the actual character value. Many of these characters are also produced by alphabetic keys when a Control key is held down.

The table below lists character constants defined in the kit and the keys they’re associated with.

Key label	Key code	Character reported
Backspace	0x1e	B_BACKSPACE
Tab	0x26	B_TAB
Enter	0x47	B_ENTER
space bar	0x5e	B_SPACE
Escape	0x01	B_ESCAPE
F1–F12 0x02 through	0x0d	B_FUNCTION_KEY
Print Screen	0x0e	B_FUNCTION_KEY
Scroll Lock	0x0f	B_FUNCTION_KEY
Pause	0x10	B_FUNCTION_KEY
System Request	0x7e	0xc8
Break	0x7f	0xca
Insert	0x1f	B_INSERT
Home	0x20	B_HOME
Page Up	0x21	B_PAGE_UP
Delete	0x34	B_DELETE
End	0x35	B_END
Page Down	0x36	B_PAGE_DOWN
up arrow	0x57	B_UP_ARROW
left arrow	0x61	B_LEFT_ARROW
down arrow	0x62	B_DOWN_ARROW
right arrow	0x63	B_RIGHT_ARROW

Several keys are mapped to the B_FUNCTION_KEY character. An application can determine which function key was pressed to produce the character by testing the key code against these constants:

B_F1_KEY	B_F6_KEY	B_F11_KEY
B_F2_KEY	B_F7_KEY	B_F12_KEY
B_F3_KEY	B_F8_KEY	B_PRINT_KEY (the “Print Screen” key)
B_F4_KEY	B_F9_KEY	B_SCROLL_KEY (the “Scroll Lock” key)
B_F5_KEY	B_F10_KEY	B_PAUSE_KEY

Note that key 0x30 P is also mapped to B_FUNCTION_KEY when the Control key is held down.

Each of the character constants listed above is a one-byte value falling in the range of values where ASCII and Unicode™ overlap. For convenience, the Interface Kit also defines some constants for common characters that fall outside that range. These characters have multibyte representations in UTF-8, so the constant is defined as a character string. For example:

#define B_UTF8_OPEN_QUOTE  "xE2x80x9C"
#define B_UTF8_CLOSE_QUOTE "xE2x80x9D"
#define B_UTF8_COPYRIGHT   "xC2xA9"

See “Character Constants” in the “General Constants” section of The Interface Kit for a full list of these constants.