DPST1091 Revision Characters Sample Solutions

Write a program parrot.c that uses scanf("%c", ...) and printf("%c", ...) to echo the user's input.

Your program should repeat this until the user enters

dcc parrot.c -o parrot
./parrot
abc
abc
ABCabc123
ABCabc123
abc
abc
xyz
xyz

When you think your program is working you can use autotest to run some simple automated tests:

1091 autotest parrot

// Read characters until eof
// Andrew Taylor - andrewt@unsw.edu.au
// 22/4/2018

#include <stdio.h>

int main(void) {
    // getchar returns an int which will contain either
    // the ASCII code of the character (if input is ASCII) or EOF

    int ch = getchar();
    while (ch != EOF) {
        putchar(ch);
        ch = getchar();
    }
    return 0;
}

Download lowercase.c here, or copy it to your CSE account using the following command:

cp -n /import/reed/A/dp1091/public_html/24T3/activities/lowercase/lowercase.c .

Your task is to add code to this function in lowercase.c:

// Returns the specified character `c`, in lowercase.
int lowercase(int c) {
    // Your code goes here!
    // Don't forget to return your result.
    return 0;
}

Here is how lowercase.c should behave after you add the correct code to the function lowercase:

dcc lowercase.c -o lowercase
./lowercase
ABC
abc
ABCabc123
abcabc123
123!@#
123!@#

When you think your program is working you can use autotest to run some simple automated tests:

1091 autotest lowercase

// Print out characters in lower case.
// A sample solution.

#include <stdio.h>

int lowercase(int c);

int main(int argc, char *argv[]) {

    // Scan in the character.
    int c = getchar();

    // Loop until there are no more characters to scan.
    while (c != EOF) {
        // Print the character, in lowercase.
        putchar(lowercase(c));

        // Get the next character.
        c = getchar();
    }

    return 0;
}

// The difference between lowercase and uppercase letters.
// If we had the letter 'A', and we added _something_ to it, we would
// get 'a' -- as the ascii values for lowercase letters are higher than
// the ascii values for uppercase letters.
//
// The _something_ that we have to add is the difference between lower
// and uppercase letters.
// e.g. 'A' + ('a' - 'A') can be rearranged to 'A' - 'A' + 'a',
// which gives us lowercase 'a'.

int lowercase(int c) {
    if (c >= 'A' && c <= 'Z') {
        return c - 'A' + 'a';
    } else {
        return c;
    }
}

Download uppercase.c here, or copy it to your CSE account using the following command:

cp -n /import/reed/A/dp1091/public_html/24T3/activities/uppercase/uppercase.c .

Your task is to add code to this function in uppercase.c:

int uppercase(int c) {
    // PUT YOUR CODE HERE

    return 0; // change to your return value
}

Here is how uppercase.c should behave after you add the correct code to the function uppercase:

dcc uppercase.c -o uppercase
./uppercase
abc
ABC
ABCabc123
ABCABC123
123!@#
123!@#

When you think your program is working you can use autotest to run some simple automated tests:

1091 autotest uppercase

// alex linker 2017-08-17
// main function for uppercase activity

#include <stdio.h>

int uppercase(int c);

int main(int argc, char *argv[]) {

    // get the character
    int c = getchar();

    // loop until end of characters
    while (c != EOF) {
        // print the character in uppercase
        putchar(uppercase(c));

        //get the next character
        c = getchar();
    }

    return 0;
}

int uppercase(int c) {
    if (c >= 'a' && c <= 'z') {
        return c - 'a' + 'A';
    } else {
        return c;
    }
}

Download swap_case.c here, or copy it to your CSE account using the following command:

cp -n /import/reed/A/dp1091/public_html/24T3/activities/swap_case/swap_case.c .

Edit the C program swap_case.c (linked above) which reads characters from its input and writes the same characters to its output with lower case letters converted to upper case and upper case letters converted to lower case.

Your program should stop only at the end of input.

which:

• returns the character in lowercase if it is an uppercase letter
• returns the character in uppercase if it is a lowercase letter
• returns the character unchanged otherwise

Note: Your program will not pass autotests if it does not contain this function.

Examples

dcc swap_case.c -o swap_case
./swap_case
Are you saying 'Boo' or 'Boo-Urns'?
aRE YOU SAYING 'bOO' OR 'bOO-uRNS'?
In this house, we obey the laws of thermodynamics!
iN THIS HOUSE, WE OBEY THE LAWS OF THERMODYNAMICS!
UPPER !@#$% lower
upper !@#$% LOWER

Assumptions/Restrictions/Clarifications

• You need only a single int variable. Don't use an array.
• Make sure you understand this example program which reads characters until end of input.
• Make sure you understand this example program which reads characters, printing them with lower case letters converted to uppercase.

When you think your program is working you can use autotest to run some simple automated tests:

1091 autotest swap_case

//  Written 3/3/2018 by Andrew Taylor (andrewt@unsw.edu.au)
//  Write stdin to stdout with upper case letters converted to lower case
// and lower case converted to upper case
//

#include <stdio.h>
#include <stdlib.h>

int swap_case(int character);

int main(int argc, char *argv[]) {
    int character = getchar();
    while (character != EOF) {
        int swapped_character = swap_case(character);
        putchar(swapped_character);
        character = getchar();
    }

    return 0;
}


int swap_case(int character) {
    if (character >= 'A' && character <= 'Z') {
        return 'a' + character - 'A';
    } else if (character >= 'a' && character <= 'z') {
        return 'A' + character - 'a';
    } else {
        return character;
    }
}