[mateo411]

The paper came out in 1972 which is the same year that C was invented. I don't think the paper mentioned what programming language was used, but since it has function calls with parameters, it's a higher level language than assembly.

[layer8]

The full KWIC index program specification can be found in the original 1971 paper (reference [8] in the 1972 paper): https://kilthub.cmu.edu/articles/journal_contribution/On_the...

The code therein uses the specification language described in https://dl.acm.org/doi/pdf/10.1145/355602.361309 (reference [3] in the 1972 paper). From there:

"The notation is mainly ALGOL-like and requires little explanation. To distinguish references to the value of a function before calling the specified function from references to its value after the call, we enclose the old or previous value in single quotes (e.g. 'VAL'). If the value does not change, the quotes are optional. Brackets ("[" and "]") are used to indicate the scope of quantifiers. "=" is the relation "equals" and not the assignment operator as in FORTRAN."

[mateo411]

Thanks for the additional context. This is very interesting.