Information Technology Reference
In-Depth Information
FIGURE 1.6
The ENIAC's first six programmers were women. Every instruction was
programmed by connecting several wires into plugboards.
(© Corbis)
from the outside. Reprogramming the computer meant removing and reattaching many
wires. This process could take many days (Figure 1.6).
Even before the ENIAC was completed, work began on a follow-on system called
the EDVAC (electronic discrete variable automatic computer). The design of the EDVAC
incorporated many improvements over the ENIAC. The most important improvement
was that the EDVAC stored the program in primary memory, along with the data manip-
ulated by the program. In 1946 Eckert, Mauchly, and several other computer pioneers
gave a series of 48 lectures at the Moore School. While some of the lectures discussed
lessons learned from the ENIAC, others focused on the design of its successor, the ED-
VAC. These lectures influenced the design of future machines built in the United States
and the United Kingdom.
During World War II, British engineer F. C. Williams was actively involved in the
development of cathode ray tubes (CRTs) used in radar systems. After the war, he de-
cided to put his knowledge to use by figuring out how to use a CRT as a storage device
for digital information. In early 1948 a team at the University of Manchester set out to
build a small computer that would use a CRT storage device, now called the Williams
Tube, to store the program and its data. They called their system the Small-Scale Ex-
perimental Machine. The computer successfully executed its first program in 1948. The
Small-Scale Experimental Machine was the first operational, fully electronic computer
system that had both program and data stored in its memory.
