I do not pretend to have any first hand knowledge of these languages, the little I know is from what can be found on the &#x27;net and, yes, second hand information. Also right now the office firewall doesn&#x27;t let me access the ALGOL Report (!). Still...<p>&quot;Garbage collection is not mentioned in ALGOL68 report at all.&quot;<p>Possibly is not mentioned explicitly, but it might be implied. Did any conforming algol implementation ship without a GC? Wikipedia explicitly lists &#x27;Cambridge ALGOL 68C&#x27; as an extension <i>omitting</i> GC. As far as I know it took a while to have a properly conforming Algol 68 compiler as the spec specifies behaviour, not implementation (cf. Knuth&#x27;s &#x27;Man or Boy Test&#x27;).<p>Also, as you pointed out, many of those languages relied on hardware support for safety. It is at least plausible that the progressive cpu intergration of the &#x27;80s which lead to the rise to dominance of simpler and faster architectures (RISCs and even x86) left languages and OSs that realied on more complex hardware support at a disavantage compared to C and UNIX.<p>It is around that time that the Lisp Machine was discontinued and the iAPX 432 failed.