INT 2F - AVATAR.SYS - SET DRIVER STATE
AX = 1A21h (AL='!')
DS:SI -> command string with one or more state characters
CX = length of command string
Return: CF set on error (invalid subfunction)
CF clear if successful
Note:   the characters in the state string are interpreted left to right, and
need not be in any particular order

Values of state characters:
'a'    activate driver
'd'    disable driver
'f'    use fast screen output
'g'    always convert gray keys (+ and -) to function keys
'G'    never convert gray keys
'l'    convert gray keys only when ScrollLock active
's'    use slow screen output
't'    Tandy 1000 keyboard (not yet implemented)

See also: 2F1A3F

2F1A21 - AVATAR.SYS - SET DRIVER STATE