Page:CTSS programmer's guide.djvu/54

 Supervisor subroutines are called by means of the trapping convention described in Chapter 3, "User Communication with the Supervisor." Where arguments are expected, they are located relative to index register 4 as in normal calling sequences; for example TSX    RDFLXA,4 PZE    BUFF,,4 . . .                 . . . RDFLXA    TIA     =HRDFLXA is a call to  with a single argument in (1,4) and a return to (2,4). The BCD name of the supervisor entry, as specified in the  instruction, must be left-justified with trailing blanks.

To read an input line from the console, TSX    RDFLXA,4 PZE    BUFF reads 14 words into memory starting at. On return the logical AC contains  where the break character is the  th character; the word containing the break has blanks to the right of the break; subsequent words contain blanks.

To issue an output line to the console, TSX   WRFLX.4  or   TSX     WRFLX,4 PZE   BUFF,,N       PZE     BUFF,,N where  writes the   words ( ≤14) starting at , adding a carriage return at the end of the line, and a color shift at beginning and end where the color shift is available; blanks are deleted from the end of the line. differs in that it does not add carriage return or color shift, and does not delete terminal blanks.

All entries to the master disk control subroutine are interpreted like supervisor calls. See Chapter 5.

The call: TSX   DEAD,4 returns control to the supervisor and puts the user in dead status, 40