In this paper, I shall explore the relationship between mathematical proof and the digital computer. This relationship is at the heart of the six scientific and technological activities shown in figure 1. Proofs are conducted about computers in at least three areas: those systems upon which human lives depend; key aspects of some microprocessors; and those systems upon which national security depends. These proofs about computers are themselves normally conducted using computer programs that prove theorems: automated theorem provers. But mathematicians themselves have also turned to the computer for assistance in proofs of great complication, and automated theorem provers are of considerable interest and importance within artificial intelligence. They raise, for example, the question of whether a computer can be an "artificial mathematician."