CS 1500 Class

Lab Assignment #11

Read sections 8.5 and 9.1 in "Tapestry" before preparing this lab.

Your job is to write a program that:

1. asks the user to specify a text file,
2. writes each string in the file backwards on the screen, on a line by
   itself.

Here is sample run:
============================================================
Script started on Sat May 08 21:31:04 1999
tester@alcyone:(~/CS1500/Lab11)	cat writBck.dat

Washington [D.C.] is
a city of Southern efficiency and Northern charm.

		-- John	F. Kennedy

tester@alcyone:(~/CS1500/Lab11)	writeBckwds
Please enter the filename: writBck.dat

notgnihsaW
].C.D[
si
a
ytic
fo
nrehtuoS
ycneiciffe
dna
nrehtroN
.mrahc
--
nhoJ
.F
ydenneK

tester@alcyone:(~/CS1500/Lab11)	exit
script done on Sat May 08 21:31:32 1999

============================================================

If you want to see a program that does a job similar to the
program you are being asked to write for this lab, look at
my_countw2.cc in this directory.

In fact, it should be quite simple to take a copy of
my_countw2.cc and transform it into a solution to this lab
problem.

The key ingredient that you need in order to solve this problem
is a loop that prints the individual characters of a string
backwards.

Section 9.1 shows how to reference individual characters in a
string.  The file spreader.cc in this directory contains code
that illustrates the kind of references your program will need to
make.

How does a program write a string backwards?  It's simple to make
a for-loop that initializes a loop-control variable to the last
character-index in a string and decrements the variable down to
zero.  Inside the loop, place a statement that writes out the
character in the string corresponding to the current value of the
loop-control variable.

GETTING IT RIGHT:

Plan your lab program during the week.  You don't have to write
it out in totally correct C++ before the lab starts.  However,
you should at least try to write a specific step-by-step
description of what your program will do.  Write this plan so
that it will be easy to translate into C++ when the time
comes.  Write some C++ statements in advance if you anticipate
having difficulty with them.  In lab, compare plans with your
partner and execute a good compromise plan.

Compile, test, and debug repeatedly until the program is
working correctly.  

Use an editor to make a small text file for testinf the program. 

If you make an error in how you write the loop code, there is a
possibility that your loop will become a "runaway" or "infinite"
loop.  If your program takes excessive time to finish, you can
force it to abort by typing a control-c.

SENDING IT IN:

When finished make a script using this command:

prompt> script lab11.script

next cat your input file.  In other words, if the input file
you made for testing your program is called

my_input

then do the command 

prompt> cat my_input

That way, the contents of your input file will be seen in the
script.  When I look at your script, I need to know what is in
your input file so that I will be able to tell if your program
got correct results.

Next run the program.  If the output is correct, then you don't
need to test any more.

After exiting the script, filter the script like this:

prompt> cat lab11.script | col -b > temp
prompt> mv temp lab11.script

Next, check that the script is OK by doing this command:

prompt> more lab11.script

Press the space bar repeatedly to see more and more of the
file, if necessary.  If the script is OK, then e-mail it to me
with this command:

prompt> mail -v -s "lab11 script" john@ishi.csustan.edu < lab11.script

PLEASE: The -s "lab11 script" part of the command above is very
        important to me.  Reproduce it exactly.

Check that the source file is OK by doing:

prompt> more writBckwds.cc

Above, you have to replace "writBckwds.cc" with whatever the name of
your source file is.

If the source file is OK then mail a copy of the source file
with a command like this:

prompt> mail -v -s "lab11 source" john@ishi.csustan.edu < writBckwds.cc

Of course, you need to replace "writBckwds.cc" with the name of
your source file if it is different.