04-more-pointer-fun/README.md

IF.03.22 Procedural Programming

Assignment More Pointer Fun

Objective

This assignment lets you practise the usage of structs, arrays and pointers to structs.

Materials

• VS Code
• gcc
• terminal.

Required Tasks

1. Create a file called pointer_fun_again.c.

2. Define a struct called PlayStruct with the following fields:

   • int_value of type integer
   • double_value of type double
   • a_string of type string (array of char of the length 64)

3. Write a main function which declares

   • a struct play_struct of type PlayStruct
   • a pointer to a PlayStruct called play_struct_pointer

4. Assign some values to the variables (you may do this already while declaring the variables). Take care how to assign a value to the pointer. What is useful/possible there?

5. Define a function print_struct which accepts the following paramters

   • a struct PlayStruct called ps
   • a pointer to a PlayStruct called pps

   The function shall print both parameters in the following form:

   • Values of struct ps: <x>, <y>, <z> where <x>, <y> and <z> shall be replaced by the actual values of the struct's fields passed to the function.
   • Values of struct pps: <x>, <y>, <z> where <x>, <y> and <z> shall be replaced by the actual values of the struct's fields passed to the function. Take care that here also the values are required to be printed although the address to pps is passed to the function.

6. Call the function print_struct in the main function and test your implementation.

7. Define a function change_struct which accepts the same parameters as print_struct. In the function body the values of the two parameters shall be changed to some different values.

8. Call the function change_struct and then again call print_struct at the end of the main function. Which values are changed, which are not? Why? Describe this briefly in a comment right after the call of your function.

9. Define a function print_string which accepts a string parameter string_to_print and prints the content of the string into the terminal.

10. Call the function print_string and pass it the field a_string of the variable play_struct. Test your implementation.

11. Define a function change_string which accepts two parameters, a string string1 and a pointer to a string p_string. The function shall change the third char of string1 and the second char of p_string to \0.

12. Call the function change_string again with the field a_string and the pointer to a newly created string another_string of length 16 which is given some initial value.

13. Finally call print_string again with the two parameters you passed to change_string before. Check the results and explain, what you observe and why. Again describe your observations in a comment after the call of the functions.

Hints

• Take care to keep the work loop "Implement a little", "Test a little" to avoid the 100 lines of error mess.

Extra Credit

Document your implementation in an extra text file or in an inline comment. In particular:

• Write down the reasons, how you assigned values to the variables in the main function.
• Give alternatives how to pass parameters when calling the different functions.
• Write down the reasons, why some variables are not changed by change_integers.

Evaluation

All coding assignments will get checked. Most common reasons that your assignment is marked down are:

• Program does not build or builds with warnings
• One or more items in the Required Tasks section are not satisfied
• Submitted code is visually sloppy and hard to read

Things to Learn

• Repeat using complex data types, like structs, arrays
• Repeat implementing functions
• Repeat pointer handling on complex data types