Mainframe Computers
Until the dawn of the personal computer in the early 1980s, computers were large, multiple
cabinet affairs that required special room conditions and trained operators and program-
mers.Mainframe computers, the larger of the computers (see Figure 1-2) can literally fill a
room. These large computers, sold by IBM, Amdahl, Unisys, Hitachi, and others, are used
to fulfill the computing needs of large companies and corporations and are also used in
large telecommunications centers. They are very powerful with huge amounts of storage
and processing capability. The drawbacks to the mainframe computer for use as a personal
computer are its size, its immense amount of computing power, and its price, which can
run into the millions of dollars.
Before the personal computer, each mainframe user worked at aterminal, which is a
device (see Figure 1-3) that combines a display monitor with a keyboard and is attached
directly to the mainframe computer by a dedicated cable. The terminal, so called because it
terminates the connection line, allows the user to send large blocks of data—the contents of
the entire display screen, actually—to the mainframe for processing, and the results are
displayed on the terminal’s monitor. The early mainframe user did not have use of a
mouse, and all data was entered as text. Graphical user interfaces (GUI) such as Microsoft
Windows or X Windows were yet to come. Today’s mainframe user is more likely to be
connected to the mainframe over a local network and to use a PC as a terminal device.
Chapter 1: The Personal Computer^5
Figure 1-2. Mainframe computers provided computing for entire companies