IN2140 v?r 2025
Oblig 1: Get to know C (Norwegian)
For norsk, se her.
In this mandatory assignment, you implement your own functions in a number of small programs to become better acquainted with the C programming language. You find the handout for this assignment here.
The tasks will be solved in the assigned teams; you can discuss solution techniques with other teams, but sharing code outside the team is not allowed. See the guidelines for mandatory tasks and other submissions at Ifi.
The examiners will test submissions on Ifi’s Linux machines, available through login.ifi.uio.no (how). Your programs must compile and run on these machines. If you have any questions about the tasks, ask your group teacher.
Answers are delivered through Devilry by Thursday, February 13 at 11:59 PM.
Task 1: Vowel Replacement
In this task, you will complete a program that replaces all vowel occurrences with another letter in a sentence.
The program takes two arguments: one sentence and one letter. All five English vowels in the sentence, i.e. ‘a’, ‘e’, ‘i’, ‘o’ and ‘u’ should be replaced with the letter. Then print the changed sentence to the terminal.
Example
$ ./vowelshift "Lorem ipsum dolor sit amet" a
Laram apsam dalar sat amat
Exercise 2: String operations
This exercise is about strings and various string operations. You should implement the following functions in the file stringsops-todo.c
Code errors in the implementation can cause segmentation faults in the program. In that case, we recommend that you use Gdb and Valgrind to find out where in the program the error occurs.
- stringsum
Write the function
int stringsum (char* s)
that takes a char pointer as an argument and returns an int value that we call the string sum. We define the string sum as the accumulated value of all characters in the string, where the value corresponds to the alphabetical position: ‘a’ has the value 1, ‘b’ has the value 2, and so on. We do not distinguish between uppercase and lowercase letters. Spaces and the terminating null byte are not included in the sum. If the string contains any characters that are not uppercase or lowercase letters or spaces, the function should return -1.
There are several ways to simplify this task; it may be a good idea to create a simple solution before improving it so that it meets all the criteria in the task.
Tip: A char is a one-byte numeric value, which can have values from -128 to 127, and is most often interpreted as a letter using the ASCII table. This can be exploited for an efficient solution – by calculating the numeric values needed to solve the problem from the ASCII values of the letters.
- distance_between
Write the function
int distance_between(char* s, char c)
which takes a char pointer and a char as arguments and returns the distance (i.e. the difference between the positions) from the first to the last occurrence of the character in the string. If the character occurs only once, the function should return 0. If the character does not occur, the function should return -1.
- string_between
Write the function
char* string_between(char* s, char c)
which takes a char pointer and a char as arguments and returns the substring that is between the first and last occurrence of the character in the string. If the character occurs only once, the function should return the empty string. If the character does not occur, the function should return the null pointer.
If the character occurs at least twice, neither the first nor the last occurrence should be included in the string you return.
Here you should NOT allocate a new string, but instead you should change the input string, and return a pointer to the correct location.
- stringsum2
Write the function
int stringsum2(char* s, int* res)
which works like stringsum, but rather than returning the string sum, it places it in the int that res points to. The function returns 0 in all cases where stringsum would return a number greater than 0. It returns -1 otherwise.
Exercise 3: The worm in the apple
You have a variable apple that is defined in the file 'the_apple.c'. The variable apple is also declared in the header file 'the_apple.h'.
The main functions of the program is located in the file apple-main.c. The functions mentioned below, which you should implemented, shall be located in the file apple-todo.c
There is only one worm in the apple, but the worm can grow large by duplicating its letters. Then it might look like this:
"leappleappleappleappwwwwooooooorrrrrrr\n"
" rrmmmmmlleappleappleappleappleappleappleap\n"
- Write the function
int locateworm(char* apple)
that finds the worm in the apple using only basic language constructs such as if … else, for, while, do, and so on—that is, no functions intended for string manipulation, such as strcpy, strchr, or strstr.
Specifically, the function should return the number that is the (zero-based) array index of the first letter belonging to the worm, or -1 if the worm does not exist.
- Write the function
int removeworm(char* apple)
that cuts out the worm from the apple by overwriting it with spaces. The function returns the length of the worm (the number of bytes that were replaced with spaces) or 0 if the worm does not exist.
Compilation
To compile the programs, we have created a specification file called CMakeLists.txt. These files are read by a software package called CMake, which can create Makefiles on Linux. It can also create project files for Visual Studio or XCode, but for IN2140 you will use terminal windows and Makefiles.
You can download and compile this project as follows: - open a terminal - in the terminal, unpack the provided files:
unzip homeexam01-handout.zip
- go into the oblig-01 directory
cd HomeExam01-Handout
- create a subdirectory to build the programs from the provided source code
mkdir build
- go into the build directory
cd build
- use CMake to create a Makefile that suits your machine
cmake ..
- compile to create executable files from the wedge code
make
- run the programs, e.g.
./vowelshift "This is a text on the command line" u
CMake is installed on login.ifi.uio.no. If you need to install CMake elsewhere, you can download it from CMake. On Windows with WSL2 and on Linux you can use Apt or Snap, on Mac Homebrew works, and on Windows with Visual Studio you can follow the instructions from Microsoft.
Delivery
You should submit your code to Devilry as an archive file. The archive file should be a Zip file and must contain all source files and documentation files.
If you follow the ‘make’ recipe under Compilation, you can create the archive file by calling
make package_source
The file is then named HomeExam01-1.0-Source.zip.