ISO 646
ISO punch tapes adopted the ASCII standard (ISO 646), an 8-bit encoding scheme that extended the character set significantly compared to ITA2. These tapes were widely used in computing environments for program storage, data transfer, and machine control.
- 8-bit ASCII:
- Encodes standard printable characters (letters, digits, symbols) and control characters.
- Provides support for up to 128 characters without a shift mechanism.
- Error Detection (Parity):
- Often, 7 bits were used for data, and 1 additional bit was reserved for parity (even or odd) to detect errors.
- Common ASCII Control Codes:
- NUL (00000000): No operation.
- ESC (00111011): Escape character for special sequences.
- BEL (00000111): Bell signal.
Physical Format of ISO Punch Tapes
- Hole Configuration:
- 8 horizontal data tracks for each bit of the byte.
- 1 sprocket hole track for alignment and feeding.
- Tape Width: 1 inch (25.4 mm).
- Row Spacing: 7.62 mm (0.3 inches).
- Larger character set enabled full alphanumeric and special characters.
- ASCII compatibility made these tapes interoperable across various systems.
- Suitable for more advanced computing and industrial automation.
Limitations of ISO Punch Tapes
- Larger size and complexity compared to ITA2.
- Limited capacity and low data density compared to emerging magnetic storage.
- Prone to tearing or damage over time.
References
- ISO 646