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TTY_DEFCHAR is a system parameter that sets the default characteristics for terminals, using a code derived by summing the following hexadecimal values:

Characteristic Value (Hex) Function
PASSALL 1 Passall
NOECHO 2 Noecho mode
NOTYPEAHEAD 4 No type-ahead buffer
ESCAPE 8 Escape sequence processing
HOSTSYNC 10 Host can send XON and XOFF
TTSYNC 20 Terminal can send XON and XOFF
SCRIPT 40 Internal use only
LOWER 80 Lowercase
MECHTAB 100 Mechanical tabs
WRAP 200 Wraparound at end of line
CRFILL 400 Perform carriage return fill
LFFILL 800 Perform line feed fill
SCOPE 1000 Terminal is a scope
REMOTE 2000 Internal use only
EIGHTBIT 8000 Eight-bit terminal
MBXDSABL 10000 Disable mailbox
NOBRDCST 20000 Prohibit broadcast
READSYNC 40000 XON and XOFF on reads
MECHFORM 80000 Mechanical form feeds
HALFDUP 100000 Set for half-duplex operation
MODEM 200000 Set for modem signals
PAGE FF000000 Page size. Default is 24

Do not set the CRFILL or LRFILL characteristic as the default in TTY_DEFCHAR.

Where a condition is false, the value is 0.

The upper byte is the page length. The default characteristics are 24 lines per page, terminal synchronization, wraparound, lowercase, scope, and full-duplex.