Java Reference
In-Depth Information
references only becomes apparent when you have multiple variables that refer to the
same object.
S
ELF
C
HECK
25.
What is the effect of the assignment
greeting2 = greeting
?
26.
After calling
greeting2.toUpperCase()
, what are the contents of
greeting
and
greeting2
?
R
ANDOM
F
ACT
2.1: MainframesÐWhen Dinosaurs
Ruled the Earth
When International Business Machines Corporation (IBM), a successful
manufacturer of punched-card equipment for tabulating data, first turned its
attention to designing computers in the early 1950s, its planners assumed that there
was a market for perhaps 50 such devices, for installation by the government, the
military, and a few of the country's largest corporations. Instead, they sold about
1,500 machines of their System 650 model and went on to build and sell more
powerful computers.
The so-called mainframe computers of the 1950s, 1960s, and 1970s were huge.
They filled rooms, which had to be climate-controlled to protect the delicate
equipment (see A Mainframe Computer). Today, because of miniaturization
technology, even mainframes are getting smaller, but they are still very expensive.
(At the time of this writing, the cost for a typical mainframe is several million
dollars.)
These huge and expensive systems were an immediate success when they first
appeared, because they replaced many roomfuls of even more expensive
employees, who had previously performed the tasks by hand. Few of these
computers do any exciting computations. They keep mundane information, such as
billing records or airline reservations; they just keep lots of them.
IBM was not the first company to build mainframe computers; that honor belongs
to the Univac Corporation. However, IBM soon became the major player, partially
because of technical excellence and attention to customer needs and partially
because it exploited its strengths and structured its products and services in a way
