This lab is due by Wednesday, October 02, 2024, Before Class.
As with all labs you may, and are encouraged, to pair program a solution to this lab. If you choose to pair program a solution, be sure that you individually understand how to generate the correct solution.
Jump To: Rubric Submission
Concepts
The focus of this assignment is on how to read data from an "input file stream" or ifstream object and write data to an "output file stream" or ofstream object.
Working with Data
Reading From Files
Today's class discussed how data is often treated as "streams" of
information that can be read a piece at a time. The files we will read
in CSCI 200 are simple text files; for lab today, the simple text file
contains a series of characters. Remember that whenever you work with a
file stream as input, we call them
ifstream
objects.
There will always be four things you will do whenever working with an
ifstream
. Open the file, check for an error, read its data, and close the file.
The typical pattern for this is as follows:
#include <iostream>
#include <fstream>
using namespace std;
int main() {
ifstream myCatsAgesIn("filename"); // declare ifstream object and open the file
// check for an error
if ( myCatsAgesIn.fail() ) {
cerr << "Error opening input file";
return -1;
}
// read the data and do something with it
int age;
while( !myCatsAgesIn.eof() ) {
myCatsAgesIn >> age;
cout << "One cat is " << age << " years old.\n";
}
myCatsAgesIn.close(); // close the file
return 0;
}
Remember, once you have an ifstream
object (like myCatsAgesIn
shown above) you use it in a manner similar to usingcin
.
Writing To Files
There will always be four things you will do whenever working with an
ofstream
.
- Open the file
- Check for an error
- Write its data
- Close the file
The typical pattern for this is as follows:
#include <fstream>
#include <iostream>
using namespace std;
int main() {
// declare ofstream object and open the file
ofstream myCatsAgesOut("filename");
// check for an error
if ( myCatsAgesOut.fail() ) {
cerr << "Error opening output file";
return -1;
}
// write the data
myCatsAgesOut << 5 << endl;
myCatsAgesOut << 8 << endl;
// close the file
myCatsAgesOut.close();
return 0;
}
Remember, once you have an
ofstream
object (like
myCatsAgesOut
shown above) you use it in a manner similar to using
cout
.
Instructions
The cows have been kidnapped by aliens! The only clue to their whereabouts is a strange "ciphered" message, stored in the file secretMessage.txt. Fortunately, our in-house cryptanalysis expert, D. Cipher, has discovered the key:
"The key isn't very advanced. To decipher the message," she
says, " you should take each character and replace all
~
(tilde) characters with a space, and shift all other characters up by one."
Your goal for this assignment is to create a program that reads the
ciphered text file and then writes a deciphered version to a file
called
decipheredMessage.txt
. For each character in the file, your program should implement the
following replacement algorithm:
- If the character read is a newline character
'\n'
, then you should write the newline character to the file. - Otherwise, if the character read is a
~
, you should write a space to the file. - Otherwise, write the character read "offset" by +1.
To see if your implementation works, you should be able to open the
file decipheredMessage.txt
and see the information about the missing cows.
Hints
Where to place the input file
Any input file needs to be placed at the project level, which should be
the same directory as your
main.cpp
file. You should see both your input file AND main.cpp file in the
same directory.
Reading whitespace characters
In order to capture and replace whitespace characters, you will not use
the
>>
operator with the input filestream. Instead, you will use the
get()
function like this:
while ( secretMessage.get(c) ) {
// c is now assigned the next character from the file
}
This example assumes your ifstream
is called
secretMessage
and you have a char
variable declared that is called c
.
Selection statement
Note that one requirement is to model the logic of the deciphering algorithm using a proper
if/else-if/else
construct. A switch
statement could also be used.
Casting to char
Remember, cout
and ofstream
objects are sensitive to the datatype of the value to be printed or written to a file. Consider the following:
cout << ('a' + 2);
What is printed to the screen? The number 99. Why? Because a char
plus an int
yields an int
, and then the int is "sent" to
cout
. To print the character c
to the screen, you will need to use casting, like this:
cout << (char)('a' + 2);
Ahhh, much better.
Grading Rubric
Your submission will be graded according to the following rubric:
Points | Requirement Description |
0.70 | Fully meets specifications |
0.15 | Submitted correctly by Wednesday, October 02, 2024, Before Class |
0.15 | Best Practices and Style Guide followed |
1.00 | Total Points |
Lab Submission
Always, always, ALWAYS update the header comments at the top of your main.cpp
file. And if you ever get stuck, remember that there is LOTS of help available.
Zip together your main.cpp, Makefile
file(s) and name the zip file L3A.zip
. Upload this zip file to Canvas under L3A.
This lab is due by Wednesday, October 02, 2024, Before Class.
As with all labs you may, and are encouraged, to pair program a solution to this lab. If you choose to pair program a solution, be sure that you individually understand how to generate the correct solution.