GTT and GTTHALT key pairs provide access to a terminal via a Tymnet circuit and perform certain terminal-related functions. These keys provide somewhat different functions than are available with other Tymnet-related keys. These keys will be implemented sooner than other Tymnet-related keys. These keys may become not available at a future time but if so a keys with very similar functions will become available. Familiarity with the Tymshare CMS and CP Assembler Users Supplement {AUS}, section Term, is assumed.

A GTT key and GTTHALT key pair correspond to a Tymnet adapter under Tymshare CP. An auxiliary circuit can not be built.

When a QUIT is received and no terminal operation is in progress, the QUIT is handled as though it were received immediately after the next terminal read or write operation is initiated. {There are no QUIT interrupts.}

GTT(GTT__READ_CHARACTERISTICS,((4,code));==>c,((4,state));) ("Read Terminal Characteristics") If "code" is invalid c will be 1. If there is no circuit present c will be 2. Otherwise c will be 0 and the state of the terminal characteristic identified by "code" is returned in "state". See BRS 10 in AUS for definition of codes.

GTT(GTT__SET_CHARACTERISTICS,((4,code),(4,state));==>c;) ("Set Terminal Characteristics") If "code" is invalid c will be 1. If there is no circuit present c will be 2. Otherwise c will be 0 and the terminal characteristic identified by "code" is set to "state". See BRS 11 in AUS for definition of codes.

GTT(GTT__SYNC,((4,timeout));==>c;) ("Synchronize with Terminal") If there is no circuit present c will be 2. Otherwise c is 0 and the operation does what BRS 12 does, waits, and returns when Device End occurs.

GTT(GTT_WRITE,((1,opts), (n,data));==>c,((4,m));) ("Output")

"Data" is sent to the terminal as with BRS 14. opts specifies options; only bits TORXLATE and TOREFOLD may be specified. n may not exceed an implementation limit of 352. After waiting for device end; c will have the ending condition from TORENDCD. Codes TOREPCK4, and TOREPCK5 cannot occur. If some or all of the data could not be output because there is no circuit, c will be 12. The possible values of c are:
0 Finished outputting data 4 VM Quit typed in 8 CP Quit typed in 12 Circuit zapped 16 Halted 20 24 28 Invalid request

m will have the number of bytes of "data" which were not output {zero unless some unusual condition terminated output prematurely}.

Where (371,parameter_list) is as follows: ((4,nll), (nll,newline), (161-nll,ignored), (1,activation set mask), (1, deferred echo mode mask), (1, opts), (4,pl), (pl,prompt), (8-pl,ignored) (4,oll), (4,olc), (oll,old line), (161-oll,ignored), (21,tab table), (1,edopt))

Data is read from the terminal as with BRS 15. Opts are option bits; only TIRXPRNT, TIRXLATE, TIRECRLF, TIRELFCR, TIRECHO, and TIREDIT may be specified. olc is the number of characters to the left of the cursor in the old line. edopt has editor option bits; only TIREDFTB, TIREDETB, TIREOPTQ, and TIREAEOF may be specified. After waiting for device end; c will be the ending condition from TIRENDCD; codes TIREPCK4, TIREPCK5, and TIREWATS cannot occur. If there is no circuit when the operation returns, c will be 12.

GTT(kt;==>c;) returns 14 (X'E') in c.

GTTHALT(0;==>c;) ("Halt Tymnet I/O") Does what BRS 13 does. c will be 1 if there was no terminal operation in progress and 0 if there was {in which case it is halted}.

GTTHALT(kt;==>c;) returns 270 {X'10E'} in c.

GTT__READ_CHARACTERISTICS=0, GTT__SET_CHARACTERISTICS=1, GTT__SYNC=2, GTT_WRITE=3, GTT_READ=4, GTT__ENABLE=5.