Card Reader - IBM 709 General Information Manual

Thus, there are 24 half-rows in the card. One full
word of binary data (including the sign) can be
punched in any half-row. The card reader regards the
punched hole as a binary 1. An unpunched hole indi-
cates a binary O. For example, a punched hole in the
8-row, card column 36, is regarded by the reader as a
binary I in the least significant position of the word
in the 8-row left. The left-most position of each half
row is reserved for the sign bit of that word (columns
1 and 37). A binary 1 represents a negative sign while
a binary 0 (no punch) represents a positive sign.
When reading or punching cards, a record is de-
fined as the information contained in one card. A
file consists of any number of cards and takes the form
of a deck. Note that the definitions of records and
files differ depending on the particular input-output
component being discussed.
Card Reader
The
IBM
711 Card Reader (Figure 88) is used by the
computer as the card input device. This reader is
available in two models. The model I reads cards at
the rate of 150 per minute while the model II reads
250 cards per minute.
Data punched in the cards may be numerical, alpha-
betic, binary, or any special character code. The inter-
pretation of the coding and reading format is con-
trolled by the stored program and the control panel
located on the reader. As a punched card proceeds
through the reader, a "card image" is built up in core
storage (Figure 89). As additional cards are read,
Figure 88.
IBM
711 Card Reader
40 IBM 709·7090
,
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1'1 lLI 'It'
Core Storage
Figure 89. Card Image in Core Storage
they too become a part of the card images stored in
core storage.
The
IBM
709 Data Processing System may have one
model II card reader attached to data synchronizer
channel A, and additional readers may be attached to
channels C and E. If a reader is attached to a data
channel, an
IBM
716 Printer must also be attached to
the same channel because it is the power source for
the reader.
The
IBM
7090 Data Processing System may have
one model II reader attached to each data channel,
making a total of eight possible readers on the system.
A printer is required for each reader.
Figure 90.
IBM
721 Card Punch