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<p>Created page with &quot;==Notes== &lt;pre&gt; Lecture 4 --------- Ideas/thoughts from group discussion on Unix - simpler, cheaper than Multics - pipes were there at the beginning and still are used - oldest form of IPC - much less emphasis on security than now (no ASLR!) - built to be modular, easy to enhance, change - programming-friendly environment - software as composition - invented inodes, had a filesystem hierarchy (which as pretty new) - kernel, shell, utilities, interesting spl...&quot;</p> <p><b>New page</b></p><div>==Notes==<br /> <br /> &lt;pre&gt;<br /> Lecture 4<br /> ---------<br /> <br /> Ideas/thoughts from group discussion on Unix<br /> - simpler, cheaper than Multics<br /> - pipes were there at the beginning and still are used<br /> - oldest form of IPC<br /> - much less emphasis on security than now (no ASLR!)<br /> - built to be modular, easy to enhance, change<br /> - programming-friendly environment<br /> - software as composition<br /> - invented inodes, had a filesystem hierarchy (which as pretty new)<br /> - kernel, shell, utilities, interesting split<br /> - abstraction in general<br /> <br /> <br /> Where was networking in Unix?<br /> - terminals, time sharing, but no networking<br /> - still being invented!<br /> (roughly at the same time)<br /> - and in fact Unix was used to build much of the early Internet<br /> <br /> Unix took over not just because it was Unix, but because it became BSD Unix which was the foundation of the early (but not earliest) Internet<br /> <br /> If you look at networking on Unix, it is different than everything else<br /> - whole separate interface<br /> <br /> <br /> How are the abstractions of Unix related to running on a single computer?<br /> - a process is fundamentally a creature of a single computer<br /> - memory is unified<br /> - pipes allow for IPC, but communication is continuous and perfect<br /> - except for broken pipes<br /> - if data gets through, it hasn&#039;t been corrupted<br /> - minimal support for mutual exclusion<br /> - no standard file locking<br /> - made implementation simpler, and programmers would know better<br /> - in general, casual assumptions of consistency and easy communications<br /> - signals in particular, no accounting for multithreaded operation<br /> <br /> Original Unix was very minimalistic, modern Unix not so much<br /> - lots of stuff bolted on over time<br /> <br /> Having to deal with Unix compatibility is a huge issue for later distibuted operating systems<br /> <br /> This has been such a burden that modern systems mostly avoid Unix semantics<br /> - it is there on individual systems but not there in the distributed context<br /> <br /> Remember Unix was made for systems we wouldn&#039;t even put in a watch today<br /> - very, very low powered by today&#039;s standard<br /> - thus very important to pick the right abstractions that allowed<br /> for minimal code<br /> - minimalism wasn&#039;t just an aesthetic, it was a necessity<br /> &lt;/pre&gt;</div>

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