4 
Figure 2 - Block Diagram of AP-C Computer 
with a precision of about one part in 128,000,000. The number of words 
stored by the computer memory can be expanded in units of 256 words 
at relatively low cost. 
For general usage, the principal means of input-output would be 
the typewriter/tape-punch/tape-reader combination, shown in the upper 
right corner of Figure 2. This unit can read tape,or type, or punch tape 
at a speed of about 15 characters per second. For the AP-C system 
application, the computer also has other means of input and output. As 
Figure 2 shows, the low-speed input-output buffer can accept infor 
mation from switches or relays and can also present information in the 
form of on-off signals to light display lamps or to energize relays. 
Finally, there is also a high-speed input-output buffer which is used in 
the AP-C system to accept inputs from the handwheels and footwheel 
and to control the servo mechanisms on the viewing unit and the 
coordinatograph. 
In summary, the AP-C control computer has about the same com 
putational capabilities as many commercial computers. The memory 
size is about the same and the variety of operations which the computer 
can perform are also roughly equivalent. In terms of speed, the AP-C