David Wheeler
Invented the subroutine call, wrote the world's first program library, and then coined the industry's most-quoted axiom.
David Wheeler (1927–2004) took his Cambridge doctorate in 1951 with what is usually counted as the first PhD in computer science anywhere. The work was done on EDSAC under Maurice Wilkes, and Wheeler supplied precisely the thing missing between "the machine can calculate" and "you can write programs for it": a repeatable way to jump into a routine and get back out. The Wheeler jump put the return address in the accumulator and let the routine plant it into its own closing jump instruction. Self-modifying code, because EDSAC had no stack to put the address on.
Once calling worked, reuse became possible, and Wheeler wrote both EDSAC's initial orders and the first library of ready-made routines. The book he published with Wilkes and Gill in 1951 was the field's first programming textbook. Much later came the Burrows–Wheeler transform and the TEA cipher. What survives in the quotation books, though, is his remark that every problem in computer science can be solved by another layer of indirection — except the problem of too many layers of indirection.