If you were a programmer in the early 1980s, you wanted to learn the spiffy new C language everyone was talking about. (And implementing on PCs — I was the proud owner of Borland’s Turbo C, version 1.0, which had so many quirks and wrinkles they were a study by themselves.) The book you learned from was Kernighan & Ritchie’s The C Programming Language. The book, like all the greatest textbooks, was universally known just by the names of its authors, as in: “Mind if I borrow your Kernighan & Ritchie over the weekend?”
Dennis Ritchie did a great deal more than merely co-write that textbook. He actually created the C language, and was instrumental in developing the UNIX operating system. Both C and UNIX have been huge influences on subsequent developments.
So we have lost two of the key figures of the Information Age within a few days of each other, and both before their time. (Ritchie was 70, which nowadays is before one’s time … I hope.)