Memory Unit: 
4032 words of command storage 
1008 words of constant storage 
404 words of data storage 
5 fast access registers of 2, 3, 5, 7, and 
9 words 
Arithmetic and Control Unit: 
Modified 5-address command structure 
6 arithmetic commands: 
Add - 165 microseconds 
Subtract - 165 microseconds 
Multiply - 165 microseconds 
Divide - 2000 microseconds 
Square root - 2000 microseconds 
3 transmit commands 
5 conditional transfer commands 
Number representation: binary, fixed point, 
fractional 
Instruction and data word length: 23 bits + 
sign 
Clock rate: 300 KC 
The above characteristics of the computer, 
combined with suitable programming, endow the 
instrument with the capacity to compute 
geographic positions to a net accuracy of about 
one part in 18,000, which is considerably better 
than the accuracy of any navigational control 
system in existence today. However, the basic 
computer itself is about ten times more accurate 
than this, allowing some margin for future 
accommodation of more accurate navigation 
systems through reprogramming and reorganization 
of input circuits, Similar considerations apply 
for other types of data to be processed, 
DIGITAL-TO-ANALOG CONVERTER AND PLOTTER 
The digital-to-analog converter converts 
binary-coded-decimal data from the computer to 
highly accurate D.C. voltages to drive the 
plotter. This conversion process takes place 
with an accuracy of about one part in 10,000. 
The servo drives in the plotter and the plotting 
mechanism itself reduce the overall plotting 
accuracy to about one part in 1,000, which on the 
30-inch plotting surface is 0.03 inch. The 
plotting accuracy is thus far less than the 
inherent digital accuracy of the instrument, but 
this is of little consequence since the digital 
data are printed and punched in code on the 
Flexowriter for whatever use one wishes to make 
of them. 
A simplified schematic diagram of the plotter 
servo system is shown in Fig. 7. The analog 
voltage from the operational amplifier in the 
digital-to-analog converter is added in series 
with the voltage across a feedback potentiometer 
which is energized from a constant voltage 
source, The resultant error voltage is chopped 
and amplified to drive a servo motor coupled to 
71 
the feedback potentiometer and to the printer 
carriage in a conventional servo loop. The servo 
is nulled and the printer carriage correctly 
positioned when the feedback voltage equals the in- 
put voltage. A similar servo is used to position 
the plotter arm on which the printer carriage 
moves. All converter and plotter circuits are 
solid-state. 
The symbol printer, shown in Fig. 8, contains 
a stamping mechanism, ribbon supply, a cross-hair 
for visual alignment, and symbol selector logic 
governing the selection of any of twelve different 
symbols, In normally automatic operation, 
plotting is performed upon command of the computer 
when plotter arm and printer carriage are sensed 
to be correctly positioned. Symbol selection 
is also normally governed by programmed 
instructions in the computer, which transmits 
the commands in accordance with the binary coding 
arrangement shown in Fig. 9. The symbols shown 
are located around the periphery of a small disc 
which also contains the conductive coding pattern. 
The symbols are selected by matching the 4-bit 
word associated with each symbol with the 
corresponding word sent by the computer. 
In automatic operation, data points relatively 
close together may be plotted as fast as once per 
second. Points separated by distances up to the 
maximum dimension of the plotting area may require 
two or three seconds, Points may also be plotted 
manually from the master control panel through 
appropriate controls for setting in data and 
energizing the symbol printer, 
OCEANOGRAPHIC USES 
With this brief description of the instrument 
itself in mind, I would like to direct, your 
attention to two possible uses of this instrument 
in oceanographic work, They are both elementary 
examples and both make use of the position 
computation mode I have described, 
In the first case, assuming the availability 
of an adequate fathometer, one has the means at 
hand to generate a bottom contour map in real 
time during a survey. As shown in Fig. 10, the 
computer can be instructed by its internal 
program to recognize preselected contour intervals 
and to plot them accordingly with chosen symbols. 
It is assumed here that corrections in either 
positional or bathymetric data can be made either 
at the source or transmitted separately to the 
computer for inclusion in the data processing. 
As fathometers and navigation systems improve, 
the resulting increase in the volume of meaning- 
ful data collected will furnish great incentive 
for this type of instrumentation, 
In the second case, shown in Fig. ll, the 
printer is modified to select numbers instead of 
abstract symbols, The result is simply a depth 
plot similar to a hydrographic smooth sheet and 
