Sad news indeed!
I have been cutting code in C and C++ since 1981 and learnt C from his perfect book "The C Programming Language" and only the other day I was teaching a commercial C Programming course (don't do so many of those now these days). After the old '70s versions of BASIC (limited to 64k of memory, that's K not M) with no real structure and stuff like Fortran, C was a breath of fresh air. I remember thinking this is what a programming language should be like and then when I moved to C++ and others, like Java, it was really a case of well they've just finished the job Ritchie started. Nearly all the programming languages in common use today, from C++ to Java to Pearl, are based on his C.
He tends to be remembered for his part in the development of UNIX but really his C programming language has had far further reaching consequences than any one operating system. In fact the whole objective of C originally was to make the UNIX operating system portable (and by extension any other operating system). In many ways you could say the C language was the start of open systems. Far more important than anything Bill Gates or Steve Jobs (RIP) ever came up with.
RIP - one of the great computing gurus.