Chapter 1 review. Are the following statements true or false? Explain why or why not.
a) A universal
machine can perform any task without anyone specifying how it is
done.
False. A program is needed; a UM can perform any
task for which one can provide a TM program. (See page 1.)
b) A universal
machine is basically just crunches numbers and spits out
fractions.
False. A universal machine is basically a symbol
manipulator. (See page 1.) For that matter, a
number is a kind of symbol.
c) Automation is
great for tedious, error-prone activities.
True. Since humans are apt to make mistakes at this sort of
task, why not have machines do it? (See page 5.)
d) A
stored-program machine stores programs in its central processing
unit (CPU).
False. The CPU executes instructions, fetching them one at
a time from programs stored in memory. (See page 6.)
e) A computer is
hard-wired to perform thousands of different primitive
instructions.
False. There are relatively few primitive instructions
hard-wired into a computer processor, but they can be combined to
perform untold numbers of possible tasks. (See page 6.)
f) A branch
instruction stores a value in a machine's instruction pointer.
True. The value tells the machine which instruction to
execute if the test condition is true (or false). (See page 7.)
g) A digital
computer stores information in bits, which are on/off states.
True. That's what makes it digital, as opposed to an analog
computer. (See page 8.)
h) A Turing
machine has a powerful "head" which reads a finite tape
faster than a speeding bullet.
False. The head can only read and write, and it's slow and
cumbersome at that. (See page 10.)
i) A universal
Turing machine can simulate any other Turing machine as a virtual
machine.
True. That's exactly why it's called a universal Turing
machine. (See page 12.)
j) RAM is a major
practical improvement of modern computers over Turing machines.
True. Data in RAM is directly and quickly accessible; Turing
machines can only access one square on a tape at a time. (See
page 13.)
k) A byte is a
string of 28 or 256 bits.
False. A byte is 23 or 8 bits, which takes on 28
or 256 possible values. (See page 14.)
l) The arithmetic
logic unit (ALU) performs instructions that are not hard-wired
into a machine.
False. It performs the instructions that are hard-wired
into the (See machine. (See page 15.)
m) A keyboard,
mouse, monitor, printer, microphones, modems, etc., are all
peripheral devices.
True. They provide input and/or output to the machine. (See page
15.)
n) A floppy disk
is ready for use as soon as you take it out of the box, just like
pizza.
False. It must be formatted first--maybe that's like
cooking a frozen pizza! (See page 15.)
o) A CD-ROM is a
write-once, read-many times medium; you can also use them to make
computers play cool music.
True. That's exactly what a CD-ROM is, but you need some extra
stuff to play music. (See page 16.)
p) A modem
converts bits into analog form for transfer over a telephone
line.
True. Data in a computer is digital, but the electrical wave that
goes over the telephone line is in analog form. (See page 16.)
q) The Internet is
a LAN.
False. A LAN is a local area network--and the Internet is
a wide area network (WAN). (See page 17.)
r) An operating
system is hardware that controls the physical devices of a
machine.
False. An operating system consists of software, not
hardware. (See page 18.)
s) An operating
system is just the program that executes commands at the request
of a user.
False. It does that, but does much more, such as managing memory,
input/output devices and processor time efficiently (See page
18.)
t) A multitasking
operating system will let many users interact with a machine at
once.
False. Multitasking allows more than one task to be
performed, but not necessarily for more than one user.
(See page 18.) For example, Windows 95 allows more
than one task to be performed, but just one user per machine at a
time.
u) A command-line
interface typically displays a prompt and waits for a user to
enter input.
True. That's the "command line"! A "prompt"
is what the system displays at the beginning of each line, such
as C:\>. (See page 18.)
v) Macintosh and
Windows are convenient command-line interfaces.
False. They are GUIs--graphical user interfaces,
emphasizing icons and menus responding to mouse events. (See page
18-19.)
w) A file is a
unit of data stored on a peripheral device such as a floppy disk.
False. A text file is a collection of data stored on a
disk--hard or floppy. (See page 19.)
x) Computers
execute programs stored in text files.
False. Programs stored in text files must be translated into
binary ("executable") files before they can be
executed. (See page 19.)
y) Directory
systems organize data in files hierarchically.
TRUE. A directory may contain files, but it may also have
subdirectories, subsubdirectories, etc.--that's where the
hierarchical structure comes in. (See page 19-20.)