Page:CTSS programmer's guide.djvu/55

 i.e., machine conditions are not saved. TSX   DORMNT,4 returns control to the supervisor and puts the user in dormant status, i.e., machine conditions and the current status of the user's program are saved, unless a command is issued which causes a new program to be read into memory. If the  command is issued, control returns to (1,4).

The call: TSX   (EFTM),4 causes entry into the floating-point trapping mode, with trapping simulated in B-core. TSX   (LFTM),4 causes exit from this mode.

The call: TSX   GETMEM,4 returns in the address of the AC the size of the user's current memory allocation. The call: TSX   SETMEM,4 sets the size of the user's memory allocation to the value in the address portion of the AC. This subroutine must be used whenever the user wishes to increase the size of his program. If he fails to do so and refers to locations outside his original memory allocation he may not cause a protection violation, since the protection indicators are set by block count rather than word count; but dumping, when users are swapped in and out of core, is done by word count, and all information stored beyond the memory bound will be lost.

The call: TSX   GETCOM,4 PZE   N returns in the logical AC the  th word of the user's latest command. Each command issued by the user is written in the supervisor region, one word per argument, in an 18-word buffer; after the last word (the last parameter in the command line) a marker is written consisting 41