HAL 9000 and the Sexadecimal Mystery - Finally Explained! | Summary and Q&A

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September 7, 2021
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Dave's Garage
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HAL 9000 and the Sexadecimal Mystery - Finally Explained!

TL;DR

Sexadecimal is a numbering system used in early computers like the ORDVAC and ILLIAC, chosen to minimize the number of bits needed to represent a digit on their paper tapes, resulting in efficient encoding and compatibility with the hardware.

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Key Insights

  • 🤔 Sexadecimal was used as the numbering system in early computers like HAL due to the hardware constraints and the need to minimize the number of bits required to represent a digit on paper tapes.
  • 🔢 Sexadecimal uses 16 digits, including KSNJFL, which can be represented by only four bits, making it more efficient for encoding data compared to ASCII and other modern encodings.
  • 🖥️ The ILLIAC computer series, including ORDVAC and ILLIAC 1, were programmed in sexadecimal and played a significant role in the development of stored-program computers.
  • ⚙️ The character set and encoding of sexadecimal were tailored to work with the Flexowriter, an electric typewriter that could produce punched tapes for input and output.
  • 📜 The choice of KSNJFL in the sexadecimal system may have been influenced by the need to distribute letters evenly across the hammer set of the typewriter to avoid jams.
  • 🔀 Sexadecimal and hexadecimal are interchangeably used in some sources, but sexadecimal specifically refers to the numbering system used in ORDVAC and ILLIAC computers.
  • 💻 The sexadecimal system allowed for the representation of two digits in a single byte and facilitated the free interspersion of control codes and data on paper tapes.
  • 🌐 The sexadecimal system's origins can be traced back to the ORDVAC/EDVAC/ILLIAC trio, which are recognized as early modern computers with binary math units and stored programs.

Transcript

Sexadecimal? Is that even a thing? You bet it is, and today in Dave's Garage, we're going to solve the sexadeximal mysteries: what sexadecimal is, where sexadecimal came from, and why sexadecimal is so weird. Plus, I clearly just enjoy saying Sexadecimal a lot. [Intro] If your parents never had the sexadeximal talk with you, you're in luck, because... Read More

Questions & Answers

Q: Why did they choose the letters KSNJFL for the sexadecimal numbering system?

The specific reason behind choosing the letters KSNJFL for the sexadecimal numbering system remains unclear. One speculation is that it might have been done to distribute the letters across the hammer set of the Friden Flexowriter typewriter more evenly, reducing the risk of hammer jams. However, further research or insights from the community could provide more definitive answers.

Q: How does sexadecimal compare to hexadecimal?

Sexadecimal and hexadecimal are similar numbering systems, but they differ in the set of digits used. Hexadecimal uses the digits 0-9 and the letters A-F, while sexadecimal uses the digits 0-9 and the letters KSNJFL. Sexadecimal was chosen for its efficiency in representing digits with only four bits, making it advantageous for encoding data on the paper tapes used in early computers.

Q: What is the significance of the ORDVAC and ILLIAC computers in relation to sexadecimal?

The ORDVAC and ILLIAC computers were early examples of machines that used the sexadecimal numbering system. They were part of the lineage of computers that adopted the von Neumann architecture, which is the foundation of modern computer systems. The use of sexadecimal in these computers allowed for efficient encoding on their paper tapes and compatibility with the hardware at the time.

Q: How does sexadecimal make use of the high bit in the character encoding?

Sexadecimal makes use of the high bit in the character encoding by assigning it to control codes such as delay, newline, and carriage return. Since the high bit is never set for binary sexadecimal data, it can be used to signal control codes without interfering with the representation of digits. This allowed for the interspersing of control codes and data on the paper tapes, providing flexibility in data storage and communication.

Summary & Key Takeaways

  • HAL, the famous computer in 2001: A Space Odyssey, was programmed in sexadecimal.

  • The ORDVAC and ILLIAC computers, which are part of the early computer lineage, were programmed in sexadecimal because it allowed for efficient encoding on their paper tapes.

  • Sexadecimal is a numbering system that uses the digits 0-9 and the letters KSNJFL, allowing for simple representation of digits with only four bits.

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