Java Reference
In-Depth Information
We've seen how a sentence of text is stored on a computer by mapping char-
acters to numeric values. Those numeric values are stored as binary numbers.
Suppose we want to represent character strings in a language that contains 256
characters and symbols. We would need to use eight bits to store each character
because there are 256 unique permutations of eight bits (2
8
equals 256). Each bit
permutation, or binary value, is mapped to a specific character.
How many bits would be needed to represent 195 countries of the world?
Seven wouldn't be enough, because 2
7
equals 128. Eight bits would be enough,
but some of the 256 permutations would not be mapped to a country.
Ultimately, representing information on a computer boils down to the number
of items there are to represent and determining the way those items are mapped
to binary values.
SELF-REVIEW QUESTIONS
(see answers in Appendix N)
SR 1.1
What is hardware? What is software?
SR 1.2
What are the two primary functions of an operating system?
SR 1.3
The music on a CD is created using a sampling rate of 44,000 mea-
surements per second. Each measurement is stored as a number that
represents a specific voltage level. How many such numbers are used
to store a three-minute long song? How many such numbers does it
take to represent one hour of music?
SR 1.4
What happens to information when it is stored digitally?
SR 1.5
How many unique items can be represented with the following?
a. 2 bits
b. 4 bits
c. 5 bits
d. 7 bits
SR 1.6
Suppose you want to represent each of the 50 states of the United
States using a unique permutation of bits. How many bits would be
needed to store each state representation? Why?
Let's examine the hardware components of a computer system in more detail.
Consider the computer described in Figure 1.8. What does it all mean? Is the sys-
tem capable of running the software you want it to? How does it compare with
other systems? These terms are explained throughout this section.
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