W. S. TOPHAM 
1221 
REAL-TIME BATCH MONITOR 
(RBM) 
5,888 
UTAH TIME-SHARING EXECUTIVE 
(UTE) 
6,187 
AUTOMATIC MONITOR 
(AUTOMON) 
6,250 
USER AREAS 
(3 @ 2K) 
6,000 
BACKGROUND 
8,191 
Figure 3. — Core map of XDS Sigma 3 computer oper- 
ating in a real-time, time-sharing mode. UTE was 
written to provide this capability and is described in 
the text. 
each remote terminal located in the Facility is 
connected to one of these interrupts, and each 
terminal should have equal priority. The execu- 
tive does use the higher level interrupts to guar- 
antee that it can perform its bookkeeping 
without being interrupted at critical times. How- 
ever, when an interrupt comes from a computer 
terminal, the time-sharing executive within a 
few hundred microseconds places the operation 
of that terminal at low priority, allowing any 
other terminal to interrupt at any time. The in- 
terrupt which controls the data sampling 
through the DATAIN subroutine is connected 
to a high-order interrupt and guarantees that 
when it is necessary to take data samples, they 
are taken at the correct time, without delay. 
The last section of core is devoted to back- 
ground activities and provides an oiT-line opera- 
tion for the computer. This includes such activi- 
ties as compilation of programs, extensive 
searches for data, hard-copy reproduction of 
data, as well as any other off-line batch jobs 
that can be accomplished in the background 
area available. 
Time-sharing in the foreground area is car- 
ried on mainly under the control of the UTE, 
and if there are no activities to be accomplished 
in the foreground, then control is relinquished 
to background. It is primarily controlled by 
RBM. At the present time, because of limited 
core space, foreground is time-shared between 
three users and the AUTOMON activities, si- 
multaneously. However, the executive has been 
written to time-share at least eight users, and 
this can also be expanded depending on the 
computation time available, as well as more 
core memory. 
Executive Subroutines 
Some of the important subroutines used by 
UTE to accomplish its data handling are the 
following : 
SCOPEWRT: This subroutine is used to 
carry out communications between the remote 
terminal and the computer. It writes the desired 
message on the screen of the terminal, plots any 
data that is desired on the terminal as governed 
by the 512 by 512 matrix capability of the ter- 
minal, and reads the information generated by 
the terminal. 
DATAIN and CLOCKINT: These subrou- 
tines are used together to provide the analog 
data sampling function. Any user can sample 
up to eight channels of analog data. It is possi- 
ble with these routines to sample those eight 
channels at any four different sample rates and 
return to the user program for computation 
after any given number of samples have been 
taken. At the present time, there are sixty-four 
analog channels connected to the computer, and 
when any sampling is done, all sixty-four chan- 
