258 | 24 TURING, lOVElACE, AND BABBAGE
There were several classes of punched card: ‘operation cards’ for instructions, ‘number cards’
for data, ‘variable cards’ to indicate where in the memory to place or retrieve data, ‘combinato-
rial cards’ to indicate how many times a particular sequence of operations should be repeated,
and so on. The machine had an internal repertoire of automatically executable functions—
direct division, multiplication, subtraction, and addition.
The range of features was dazzling: there was a separate ‘store’ (memory) and a ‘mill’ (proces-
sor). At machine level, ‘microprograms’ automatically executed each of the internal repertoire
of instructions: these microprograms were coded onto ‘barrels’ with moveable studs like those
on a barrel organ, but substantially larger. The machine was capable of iterative looping, con-
ditional branching, parallel processing, anticipating carriage, transferring data on a multidigit
parallel bus or data highway, and output in various forms including printing, stereotyping,
graph plotting, and punched cards.^12 Serial operation using a fetch–execute cycle, the separa-
tion of store and mill, and the input–output arrangements of the Analytical Engine are signa-
ture features of the so-called ‘von Neumann architecture’, as described by John von Neumann
in his classic paper in 1945, and which has dominated computer design since.^13
Ada lovelace
The machine conceived and designed by Babbage was an engine for doing mathematics, the
driving preoccupation of its inventor—finding the value of any mathematical expression, tabu-
lating functions, solving partial differential equations, enumerating series, and so on. In 1836
Babbage hinted at the prospects of a general-purpose algebraic machine able to manipulate
symbols ‘without any reference to the value of the letters’, but he described the idea as ‘very
indistinct’ and did not elaborate.^14 Symbolic algebra was an abiding aspiration and he returned
to this later with some success. The context throughout was nonetheless mathematical.
The transition from calculation to computing, or from number to symbol, was articulated
more clearly by Ada Lovelace, Lord Byron’s daughter from his short-lived and troubled mar-
riage to Annabella Milbanke. Lovelace (Fig. 24.4) and Babbage met in 1833 when she was 17
figure 24.4 Ada Lovelace.
Alfred Edward Chalon. Posted to Wikimedia
Commons and licensed under public domain,
https://en.wikipedia.org/wiki/Ada_Lovelace#/
media/File:Ada_Lovelace_portrait.jpg.