One of the things I remember from my computer science classes at Berkeley is Dijkstra's Algorithm, used to solve for the shortest distance between a source and a destination. It's an elegant algorithm that even an ignorant undergraduate was able to grasp, yet it is powerful enough to determine the distance from a single point to ALL other points on a graph. This algorithm drives many modern day processes such as laying out circuit boards or routing through large networks.
Dijkstra's name appeared in many of the textbooks and research papers I read at the university and I ended up doing research into his ideas about semaphores and file locking in real time operating systems. The debate E.W. Dijkstra led about structured programming and the abolition of the GOTO statement modernized the way computer programming was done.
On Tuesday, Edsger Wybe Dijkstra, a giant in Computer Science, died.