IBM 726
Encyclopedia
The IBM 726 dual magnetic tape reader/recorder for the IBM 701
was announced on May 21, 1952. Unlike later IBM 7 track drives, the 726 could read backwards as well as forwards.
The tape had seven parallel tracks
, six for data (called a copy group, not a character) and one to maintain parity
. Tapes were recorded in odd parity, to ensure at least one bit transition per
copy group as well as for error checking.
IBM 701
The IBM 701, known as the Defense Calculator while in development, was announced to the public on April 29, 1952, and was IBM’s first commercial scientific computer...
was announced on May 21, 1952. Unlike later IBM 7 track drives, the 726 could read backwards as well as forwards.
The tape had seven parallel tracks
IBM 7 Track
IBM's first magnetic tape data storage devices, introduced in 1952, use what is now generally known as 7 track tape. The magnetic tape is 1/2" wide and there are 6 data tracks plus 1 parity track for a total of 7 parallel tracks that span the length of the tape...
, six for data (called a copy group, not a character) and one to maintain parity
Parity bit
A parity bit is a bit that is added to ensure that the number of bits with the value one in a set of bits is even or odd. Parity bits are used as the simplest form of error detecting code....
. Tapes were recorded in odd parity, to ensure at least one bit transition per
copy group as well as for error checking.
| Tracks | 6 Data, 1 parity |
|---|---|
| Copy groups/inch | 100 copy groups/inch |
| Tape speed | 75 Inches/sec |
| Transfer rate | copy groups/sec |
| End of record gap | 1 Inch - 100 chars - 16.67 words |
| Start time | 10 ms |
| Stop time | 10 ms |
| Width of tape | 1/2 inch |
| Length of reel | |
| Composition | Cellulose acetate base |