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2.1 / A BRIEF HISTORY OF COMPUTERS 29

components—transistors, resistors, capacitors, and so on. Discrete components were
manufactured separately, packaged in their own containers, and soldered or wired
together onto masonite-like circuit boards, which were then installed in computers,
oscilloscopes, and other electronic equipment.Whenever an electronic device called
for a transistor, a little tube of metal containing a pinhead-sized piece of silicon had
to be soldered to a circuit board. The entire manufacturing process, from transistor
to circuit board, was expensive and cumbersome.
These facts of life were beginning to create problems in the computer industry.
Early second-generation computers contained about 10,000 transistors. This figure
grew to the hundreds of thousands, making the manufacture of newer, more power-
ful machines increasingly difficult.
In 1958 came the achievement that revolutionized electronics and started the
era of microelectronics: the invention of the integrated circuit. It is the integrated
circuit that defines the third generation of computers. In this section we provide a
brief introduction to the technology of integrated circuits. Then we look at perhaps
the two most important members of the third generation, both of which were intro-
duced at the beginning of that era: the IBM System/360 and the DEC PDP-8.
MICROELECTRONICS Microelectronics means, literally, “small electronics.” Since
the beginnings of digital electronics and the computer industry, there has been a
persistent and consistent trend toward the reduction in size of digital electronic cir-
cuits. Before examining the implications and benefits of this trend, we need to say
something about the nature of digital electronics. A more detailed discussion is
found in Chapter 20.
The basic elements of a digital computer, as we know, must perform storage,
movement, processing, and control functions. Only two fundamental types of com-
ponents are required (Figure 2.6): gates and memory cells.A gate is a device that im-
plements a simple Boolean or logical function, such as IF A AND B ARE TRUE
THEN C IS TRUE (AND gate). Such devices are called gates because they control
data flow in much the same way that canal gates do.The memory cell is a device that
can store one bit of data; that is, the device can be in one of two stable states at any
time. By interconnecting large numbers of these fundamental devices, we can con-
struct a computer.We can relate this to our four basic functions as follows:

• Data storage: Provided by memory cells.
• Data processing: Provided by gates.

• Boolean Binary
Input • logic Output Input storage Output
• function cell

Read
Write
Activate
signal
(a) Gate (b) Memory cell
Figure 2.6 Fundamental Computer Elements