Overview
ISO 1113:1979 specifies the representation of the 7-bit coded character set on punched tape 25.4 mm (1 in) wide. The standard is intended for use in conjunction with ISO 646 (the 7-bit character set), ISO 1154 (dimensions and locations of feed and code holes) and ISO 1729 (specification for unpunched tape). It establishes a clear, interoperable layout for encoding characters on punched tape with an added parity bit for basic error protection.
Key Topics
- Tape width and materials: Applies to punched tape 25.4 mm (1 in) wide; physical hole dimensions and locations are specified in ISO 1154.
- Track layout and numbering: Code tracks are numbered consecutively from 1 to 8 starting at the reference edge. The feed-hole track runs parallel to the tape edges and separates code tracks; the feed hole track is located between code tracks 3 and 4.
- Bit-to-track assignment: Bits b1 to b7 of each 7-bit character are assigned respectively to tracks 1 through 7. The standard maps each bit position to a fixed track to ensure consistent encoding and decoding.
- Parity bit: An extra bit (the parity bit) is added in track 8. The parity is even, i.e., the parity bit is chosen so that the total number of binary ONEs in the transverse row is even. This provides simple error detection for punched-row errors.
- Representation convention: The absence of a hole represents binary ZERO; the presence of a hole represents binary ONE. Each transverse row of holes encodes a single character and its parity bit.
- Direction and reference edge: The reference edge is the side with three code holes (the side opposite the feed-hole track). The tape movement direction is defined as opposite to the character sequence; this clarifies punch and read direction for devices.
Applications
- Legacy data interchange: Ensures consistent encoding when transferring text and control data between punched-tape systems using the ISO 646 character set.
- Archival and recovery: Useful for reading or reproducing historical punched-tape media where precise track mapping and parity conventions are required.
- Interoperability: Facilitates reliable communication between equipment and software that implement ISO 646 and physical tape specifications (ISO 1154 / ISO 1729).
Related Standards
- ISO 646 - 7-bit coded character set for information processing (character repertoire and code points).
- ISO 1154 - Punched paper tape: dimensions and locations of feed and code holes (physical hole and track specifications).
- ISO 1729 - Unpunched paper tape specification (physical tape characteristics).
Using ISO 1113:1979 alongside these referenced standards ensures a complete, interoperable framework for representing 7-bit characters on punched tape, with track assignment and even-parity error protection to support robust data interchange.