‘

CHAPTER 24

Turing, Lovelace, and Babbage

doron swade

T

he principles on which all modern computing machines are based were enunciated
more than a hundred years ago by a Cambridge mathematician named Charles
Babbage.’ So declared Vivian Bowden—in charge of sales of the Ferranti Mark I
computer—in 1953.1 This chapter is about historical origins. It identifies core ideas in
Turing’s work on computing, embodied in the realisation of the modern computer. These
ideas are traced back to their emergence in the 19th century where they are explicit in the
work of Babbage and Ada Lovelace. Mechanical process, algorithms, computation as system-
atic method, and the relationship between halting and solvability are part of an unexpected
congruence between the pre-history of electronic computing and the modern age. The chap-
ter concludes with a consideration of whether Turing was aware of these origins and, if so, the
extent—if any—to which he may have been influenced by them.

Introduction

Computing is widely seen as a gift of the modern age. The huge growth in computing coincided
with, and was fuelled by, developments in electronics, a phenomenon decidedly of our own
times. Alan Turing’s earliest work on automatic computation coincided with the dawn of the
electronic age, the late 1930s, and his name is an inseparable part of the narrative of the pion-
eering era of automatic computing that unfolded.
Identifying computing with the electronic age has had the effect of eradicating pre-history.
It is as though the modern era with its rampant achievements stands alone and separate from
the computational devices and aids that pre-date it. In the 18th century lex continui in natura
proclaimed that nature had no discontinuities, and we tend to view historical causation in the
same way. Discontinuities in history are uncomfortable: they offend against gradualism, or at
least against the idea of the irreducible interconnectedness of events.
The central assertion of this chapter is that core ideas evidenced in modern computing,
ideas with which Turing is closely associated, emerged explicitly in the 19th century, a hundred
years earlier than is commonly credited. While this assertion may come as no great surprise to
many, the detailed extent to which it applies is perhaps less fully appreciated than the evidence