COMP1721 - Higher Computing 1B

This lab involves:

• Simple input of strings.

• Manipulating strings and characters.

Create a separate directory (lab04 is a good name) using mkdir for this week's lab exercises.

Exercise 1: Printing Characters One Per Line

For example:

% a.out
Enter string: Hello
H
e
l
l
o

Exercise 2: Palindrome

Write a program, palindrome.c, which reads a string and tests if it is a palindrome.

For example:

% a.out
Enter possible palindrome: kayak
String is a palindrome
% a.out
Enter possible palindrome: canoe
String is not a palindrome

Design

Exercise 3: Modifying Palindrome

For example:

% a.out
Enter possible palindrome: Do geese see God? 
String is a palindrome
% a.out
Enter possible palindrome: Do ducks see God?
String is not a palindrome
% a.out
Enter possible palindrome: Madam, I'm Adam
String is a palindrome
% a.out
Enter possible palindrome: Madam, I'm Bruce
String is not a palindrome

Exercise 4: Letter Frequencies

Why might you want to do this? In the past, scholars of literature have actually used gross statistics of pieces of text, such as letter frequencies, to solve controversies over authorship.

The file data contains example input for your program. Save it in your directory. Its contents are:

This is a little file of text.
It's called "data".
It has 6 lines of input.

I'm going to use it for testing the
letter count program I've just written.

When given data as input this is how your program should behave.

% a.out
hello world
<control-d>
1 lines of input read.
10 alphabetic characters read.
2 non-alphabetic characters read.
The frequencies of the alphabetic characters was:
'd' 1
'e' 1
'h' 1
'l' 3
'o' 2
'r' 1
'w' 1
% a.out <data
6 lines of input read.
112 alphabetic characters read.
41 non-alphabetic characters read.
The frequencies of the alphabetic characters was:
'a' 6
'c' 2
'd' 2
'e' 12
'f' 4
'g' 4
'h' 3
'i' 14
'j' 1
'l' 7
'm' 2
'n' 6
'o' 7
'p' 2
'r' 5
's' 8
't' 20
'u' 4
'v' 1
'w' 1
'x' 1

This output tells us that, for example, the letter 't' occurs 20 times in the text while the letter 'z' doesn't occur anywhere.

You should quickly check that the program has done the right thing, by hand counting some of the characters above in the text and making sure that your count agrees with what the program produced.

There are a couple of things to observe about the way this program behaves. First, it treats 't' and 'T' as being equivalent; there is a 'T' in the data file, but it has been counted towards the overall count of 't's, if you check by hand.

Second, it counts in a separate category anything else that's not a letter of the alphabet, including digits.

Third, it doesn't print zero counts.

Finally, note very carefully the output format that the program uses; we want your program to produce its output in exactly the same format.

Hints

Finished?

When you are sure all are working submit them using give. Here is the command to use:

% /home/cs1721/bin/classrun -give lab04 one.c palindrome.c frequency.c

This will run some simple tests.

Then get your tutor to check your answers are correct and give you the lab mark for this week.