; Stable assembly ABI exported by the resident BIOS at C000.
BIOS_PUTC       = 0xC050 ; A = character; preserves all registers
BIOS_TRY_GETC   = 0xC053 ; returns A = character or 0; preserves BC..IY
BIOS_GETC       = 0xC056 ; blocking; returns character in A
BIOS_IO_OUT     = 0xC059 ; A = port, L = value; preserves all registers
BIOS_IO_IN      = 0xC05C ; A = port; returns value in A
BIOS_DELAY_MS   = 0xC05F ; HL = milliseconds; preserves all registers
BIOS_MONITOR    = 0xC062 ; warm-start the monitor; does not return