C was already implemented on several quite different machines and OSs, Unix was already being distributed on the PDP-11, but the portability of the whole system was new.
Meaning of the quote
The quote is saying that the programming language C and the operating system Unix were already being used on different types of computers and systems, but the ability to easily move or "port" the entire system to work on other computers was a new and important development.
More quotes from Dennis Ritchie
C was already implemented on several quite different machines and OSs, Unix was already being distributed on the PDP-11, but the portability of the whole system was new.
{mb_by_description:plain}
The visible things that have come from the group have been the Plan 9 system and Inferno, but I hasten to say that the ideas and the work have come from colleagues.
{mb_by_description:plain}
Any editing, software work, and mail is done in this exported Plan 9.
{mb_by_description:plain}
I’m not a person who particularly had heros when growing up.
{mb_by_description:plain}
UNIX is basically a simple operating system, but you have to be a genius to understand the simplicity.
{mb_by_description:plain}
Obviously, the person who had most influence on my career was Ken Thompson.
{mb_by_description:plain}
I can’t recall any difficulty in making the C language definition completely open – any discussion on the matter tended to mention languages whose inventors tried to keep tight control, and consequent ill fate.
{mb_by_description:plain}
At least for the people who send me mail about a new language that they’re designing, the general advice is: do it to learn about how to write a compiler.
{mb_by_description:plain}
Over the past several years, I’ve been more in a managerial role.
{mb_by_description:plain}
C++ and Java, say, are presumably growing faster than plain C, but I bet C will still be around.
{mb_by_description:plain}
A new release of Plan 9 happened in June, and at about the same time a new release of the Inferno system, which began here, was announced by Vita Nuova.
{mb_by_description:plain}
The kind of programming that C provides will probably remain similar absolutely or slowly decline in usage, but relatively, JavaScript or its variants, or XML, will continue to become more central.
{mb_by_description:plain}
When I read commentary about suggestions for where C should go, I often think back and give thanks that it wasn’t developed under the advice of a worldwide crowd.
{mb_by_description:plain}
At the same time, much of it seems to have to do with recreating things we or others had already done; it seems rather derivative intellectually; is there a dearth of really new ideas?
{mb_by_description:plain}
I fix things now and then, more often tweak HTML and make scripts to do things.
{mb_by_description:plain}
I’m just an observer of Java, and where Microsoft wants to go with C# is too early to tell.
{mb_by_description:plain}
I’ve done a reasonable amount of travelling, which I enjoyed, but not for too long at a time.
{mb_by_description:plain}
C is peculiar in a lot of ways, but it, like many other successful things, has a certain unity of approach that stems from development in a small group.
{mb_by_description:plain}
For infrastructure technology, C will be hard to displace.
{mb_by_description:plain}