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.
b) A universal machine basically
just crunches numbers and spits out fractions.
False. A universal machine is basically a symbol manipulator. For that matter, a number is a kind of symbol.
c) Automation is great for tedious,
True. Since humans are apt to make mistakes at this sort of task, why not have machines do it?
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.
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.
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).
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.
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.
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.
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.
l) The CPU executes instructions
that are not hard-wired into a machine.
False. The CPU or central processing unit, is the actual processor of the machine. It performs the instructions that are hard-wired into its arithmetic/logic unit (ALU).
Note: the book has two sets of review j, k, and l for this chapter. Answers for the second set below:
j') A keyboard, mouse, monitor,
printer, microphones, modems, etc., are all peripheral devices.
True, these peripheral devices, outside the computer case, provide input and/or output to the machine.
k') 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!
l') A CDROM is a write-once, read-many
True for most CDROMs, i.e., once a computer writes data on a CDROM, you can erase or add more data. There are asl CDRW disks, which allow you to write more than once, but there are a bit more expensive.
m) 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.
n) The Internet is a LAN.
False. A LAN is a local area network--and the Internet is a wide area network (WAN).
o) An operating system is hardware
that controls the physical devices of a machine.
False. An operating system consists of software, not hardware.
p) 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
q) 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. For example, Windows 95 allows more than one task to be performed, but just one user per machine at a time.
r) 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:\>.
s) Macintosh and Windows are convenient
False. They are GUIs--graphical user interfaces, emphasizing icons and menus responding to mouse events.
t) 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.
u) 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.
v) 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.