The task is to check that the terminal supports Unicode output, before outputting a Unicode character. If the terminal supports Unicode, then the terminal should output a Unicode delta (U+25b3). If the terminal does not support Unicode, then an appropriate error should be raised.

Note that it is permissible to use system configuration data to determine terminal capabilities if the system provides such a facility.

/* terminal_control_unicode_output.wren */
 
class C {
    foreign static isUnicodeSupported
}
 
if (C.isUnicodeSupported) {
    System.print("Unicode is supported on this terminal and U+25B3 is : \u25b3")
} else {
    System.print("Unicode is not supported on this terminal.")
}