in the interview, kernighan said, 'The main idea in Awk was associative arrays, which were newish at the time, but which now show up in most languages either as library functions (hashmaps in Java or C++) or directly in the language (dictionaries in Perl and Python). Associative arrays are a very powerful construct, and can be used to simulate lots of other data structures.'

zambyte expressed surprise that kernighan referred to 'associative arrays' as 'newish' and said that lisp had had them 20 years before. what lisp had 20 years before (presumably they meant in https://www-formal.stanford.edu/jmc/recursive.pdf in 01959, not 01957, when mccarthy was trying to figure out how to add linked lists to fortran) was this line of code:

assoc[x; y] = eq[caar[y]; x] → cadar[y]; T → assoc[x; cdr[y]]

which we can translate to python as

assoc = lambda x, y: y[0][1] if y[0][0] == x else assoc(x, y[1:])

and which allows you to use a list of 2-tuples such as [('red', '#f00'), ('green', '#0f0'), ('white', '#fff')] as an associative array

you replied, saying, 'it was (...) easy to be (...) knowledgeable and yet never have been exposed (...) in the 1990s (...) I can tell you a lot of the C world would still consider associative data structures like a hash table something to be a bit exotic (...). It was very easy to not be very up to date on these things.'

that comment is only relevant to zambyte's comment—to which you posted it as a reply—if you had the implicit assumption that what kernighan meant by 'associative arrays' was 'associative data structures like a hash table'. but associative data structures like hash tables were not newish; hash tables in particular were 22 years old in 01979, and were already the most commonplace of all data structures except for strings and arrays. i listed 13 articles in cacm in 01975 and 01976 about associative data structures. cacm only published about 6 articles per issue (excluding the news and opinion departments), so that's roughly 10% of everything they published

you say 'you can't prove the normal world of computing was all aware of all these things', but the everyday world of computing was, if anything, even more preoccupied with associative data structures than the academic world. ibm's most lucrative product was ims, an online database, which is to say, a large on-disk associative data structure. filesystems (including dectapes), variable namespaces in interpreters and compilers, symbol tables (in assemblers, linkers, and compilers), and databases are associative arrays. even in 01979 it was already hard to find programmers who did not use any of filesystems, assemblers, interpreters, or databases (though they did exist)

so it is completely implausible that what kernighan was describing as 'newish' (in 01979) was associative data structures like a hash table. i'm not doubting you when you say you knew c programmers in the 90s who considered them 'exotic', perhaps the province of the wizards who wrote compilers and filesystems, but those c programmers were not 'the normal world of computing' or 'experienced and knowledgeable'; they were beginners

the 01978 edition of k&r presents binary search (using a sorted array as an efficient associative array) in chapter 3 on p. 54 (62/236), before presenting such advanced language features as the 'break' statement, '#define', structs, non-integer function return values, and pointers. in chapter 6 on p. 125 (133/235), they use such an associative array to count the number of times each c keyword occurs in the input. §6.5 (pp. 130–134 (138–142/235)) demonstrates a more scalable associative array using a binary search tree. §6.6 (pp. 134–136 (142–144/235)) gives another program using a hash table

so for k&r in 01978, hash tables were more basic than features such as unions, typedef, string formatting (%.10s, etc.), opening files, and listing directories, all of which are relegated to later in the book

please don't tell me 'a lot of the c world' in the 01990s hadn't heard of k&r. next you're going to be telling me a lot of the c world hadn't heard of c

getting back to the interview, what kernighan was evidently referring to was not associative array data structures in general, but having a general-purpose associative data structure library always at hand. lisp's assoc (or assq) isn't general-purpose because it's too slow for large associative data structures. lisp plists aren't general-purpose because they leak memory (you can't remove a property from all atoms, and each atom you put a property on continues to occupy memory even if you remove the property from it) and because they get too slow if you have more than a few properties. ims isn't general-purpose because you have to go talk to the database administrator to create a new file; you can't create a temporary one in ram. the example hash table in k&r isn't general-purpose because it uses a static array, a fixed size of 100 hash buckets, has no deletion, associates specifically a string value with each (string) key, and is quite inefficient; it's a reasonable starting point, but you have to tweak it for your application

java hashmaps, awk arrays, and python dicts are general-purpose as long as your data fits in ram. (you could gripe that awk arrays aren't first-class objects and can only have string and numeric keys, but that's just because awk doesn't have first-class objects at all in the lisp sense.)

precisely as a result of this, hashing (like sorting) has ceased to be a beginner-programmer topic; if you need an associative array or a sorted list, you can get quite far just by invoking the built-in facilities of your programming language. sooner or later you will probably want one optimized for some specific application, but it's no longer something you have to do all the time. but to any working programmer in the 01970s, it would have seemed absurd to propose linear searches or hash tables were 'newish'