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2030 Processing Unit
Main
Storage
Input/
r--~
Output
Channel
Control
Unit
Random
Access
Device
Control
Unit
Random
Access
Device
Data and Control Information .....
i-----..
Arithmetic,
Control, and
Register
Systems
Control
Unit
Figure 1-7.
Typical Data Processing System
Primary Storage
•
The smallest main storage addressa-
ble unit is called the byte.
•
•
•
•
•
•
A byte consists of 8 data bits and 1
parity bit.
Cdd parity is main-
tained.
The System/360 uses a 24 bit binary
address.
A byte can represent characters,
binary numbers, or many different
codes.
A half word is 2 bytes.
A word is 4 bytes.
A double word is 8 bytes.
•
•
•
Control Unit
Printer
Data can be fixed length (2, 4, or 8
bytes) or variable length (up to 256
bytes) •
Fixed length data must reside on the
correct boundaries in main storage.
A program check occurs if the bound-
ary restriction is violated.
The primary storage is that section of a
computing system that contains the pro-
gram to be executed as well as the data
to be processed.
All data entering the
system goes into the primary storage
before it can be processed.
After proc-
essing, the data must be placed back
into primary storage before it can be
sent to an output device.
1-9
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