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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 "Global Variables, Constants, and Defined Types" section of The Interface Kit for a full list of these constants.


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