In the 1930s, Alan Turing developed the concept of a universal Turing machine that could simulate any other Turing machine by reading the description of that machine from its tape. This established the idea that computer programs are just descriptions of logic that can be run on any universal machine. Thus, in developing this concept to formalize the limits of mechanical computation, Turing accidentally invented the fundamental idea of software as a set of instructions that can be run on different hardware platforms.

1. Presented by Melvin Zhang
melvinzhang@gmail.com
@melvinzhangzy
Turing and the Typewriter
How Alan Turing accidentally invented Software
http://tiny.cc/turing-typewriter

2. https://oztypewriter.blogspot.com
Turing in 1923

3. http://www.kurzweilai.net/passing-of-the-typewriter

5. A precise definition of computation

6. http://aturingmachine.com/

7. An example of Turing’s automatic machine

8. Demo: Running Turing’s a-machine

9. Computation = Turing Machine
Turing’s Thesis

10. Kurt G¨odel
“That this really is the correct
definition of mechanical
computability was established
beyond any doubt by Turing.”

11. A problem which cannot be solved by
Turing machines

12. “It is possible to invent a
single machine which can be
used to compute any
computable sequence.
If this machine U is supplied
with a tape on the beginning
of which is written the S.D.
of some machine M, then U
will compute the same
sequence as M.”
Alan Turing in 1936

13. Software = description of machine M

14. Software = description of machine M
U(description of M) = M()

15. Demo: Running U on a description of M

16. “If it should turn out that the basic logics of
a machine designed for the numerical
solution of differential equations coincide
with the logics of a machine intended to
make bills for a department store, I would
regard this as the most amazing coincidence
that I have ever encountered.”
Howard Aiken in 1956

17. Building a physical Turing machine

18. Automatic Computing Engine,
proposed in 1946 and built in 1950

19. Turing’s accidental invention of software
• machines can be described on the tape
• and executed on the universal machine U
• software = description of some machine M

20. Turing’s accidental invention of software
• machines can be described on the tape
• and executed on the universal machine U
• software = description of some machine M
References
http://tiny.cc/turing-typewriter