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3 - Six Bit BCD Characters in Memory
Tape
118
Movement
·~
17
16
15
14
13
12
11
10
9
8
7 6
5
4
3
2
1
t
t
13
14
15
16
17
18
p
~
7
8
9
10
11
12
p
~
1
2
3
4
5
6
p
........
....
~
P is a generated
~
parity bit for each character
Binary Mode
During binary mode operations, 18 bits (1-18) are written on tape as three lines of information.
Tape
Movement
13
14
15
16
17
18
p
7
8
9
10
11
12
p
1
2
3
4
5
6
p
18 - Bit Binary Word in Memory
118
17
16
15
14
13
12
11
10
9
8
7 6
~
~
t
J
P is a generated odd parity bit for each line of
binary information
5
4
3
2
1
I
The format of information on tape in the binary mode is the same as in the decimal mode. In
the binary mode, however, the zone bits and 0 are not altered during the transfer of information.
Also, in the binary mode, the parity bit P generated for each line on tape is an odd parity bit.
Record Length
After reading (in binary or decimal mode) N words from magnetic tape into memory starting
at location M, memory location M + N will contain zeros if exactly N words were read from a
record on tape containing N words.
If
the number of words contained in the record currently
read is less than N, then only the contents of the record will be stored in memory and the 2' s
complement of the difference (N - record length) will be stored in memqry cell M + N with a
1-bit in position 18.
If
the number of words in the record is greater than N, then only N words
will be stored in memory and the increment (record length - N) will be stored in memory cell
M + N with a 0 in the sign position. M is not automatically modified. In order to forward space
(skip) one record, the RTS, RTD, or RTB command is used with N set equal to 0. This statement
[ID£1J&~~1JCJ ~@------------
V-45
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