Programming instructions

ARITHMETIC
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IMTERFACE
*Included in B
Standard PDP-4
Figure 1 - PDP-4 System with Real-Time Connection
ARITHMETIC AND CONTROL ELEMENT
The Operator Console, Internal Processor, and Core Memory constitute
the Arithmetic and Control Element. The Internal Processor carries out
the arithmetic and logical operations and controls the Real-TimeConnec-
tion and the Core Memory. Binary arithmetic with a fixed point is employed.
The optional Extended Arithmetic Control Unit, Type 22, gives PDP-4 a
multiply, divide, and arithmetic shifting capability without the use of sub-
routines.
The Console is used to observe and control the action of the program and
the Internal Processor, and to alter the contents of Internal Prncessor
registers. The contents of Core Memory can be examined or new infor-
mation deposited.
All Internal Processor registers are displayed
continuously.
Memory capacities of from 1,024 to 32,768 words are available for PDP-4.
The cycle time (the time required to read information from memory and
rewrite information back into memory) is 8 microseconds. The access
time (the time required to read information from memory) is 2 micro-
seconds. In the event of power failure, the contents of the Core Memory
remain unaltered. See Chapter 2 for detailed functions of the Arithmetic
and Control Element.
INTERFACE
The Real-Time Connection, furnished as standard equipment, provides
communication between the Internal Processor and the Perforated-Tape
Reader, the Perforated-Tape Punch and Control, Type 75, and the Printer-
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