COMP 321 Lab 1

# COMP 321 Lab 1

## Alan Cox and Scott Rixner

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<footer><em>COMP 321 Spring 2025 • Alan Cox and Scott Rixner</em></footer>

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# Remember COMP 222!

* C
* GitHub and GitHub Classroom
* CLEAR9

Review the COMP 222 information on [GitHub and CLEAR](https://www.clear.rice.edu/comp222/html/laboratories/lab01/)

Link your NetID to your GitHub account in GitHub Classroom

Remove your `.vscode-server` directory on CLEAR9 to remove any remnants of your COMP 222 environment

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# Lab Expectations

* Show up to lab!
* Complete the exercises
* Collaborate: work with each other
* Ask questions

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# Lab Extra Credit

* Completing the lab material is **strongly** encouraged
  * Directly useful in the homework assignments
  * May be on the exams
* Attendance will be taken at every lab
* If you attend all of the labs, you will receive extra credit
  * Grade bump if you are within 0.25 points of the next letter grade
  * 3 "pre-excused" absences for any reason (sick, traveling, etc.)
  * No need to contact the instructors to use these absences

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# Code Style

* Code style is important
* Always use a consistent style
* Follow the COMP 321 <a href="../../style.html">Style Guide</a>

First and foremost rule of good coding style:

> The style of your code, e.g., its indentation, should match the style of the surrounding code.

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# Today: Dynamic Arrays in C

Build an array abstraction in C that:
  * Can grow and shrink dynamically
  * Can store elements of any type

Underlying storage should:
  * Be allocated on the heap in contiguous memory
  * Double in size when full
  * Half in size when less than 1/4 full
  * Be deallocated when the array is freed

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# Dynamic Arrays in C

```
typedef struct DynamicArray DynamicArray;

DynamicArray *dynarray_create(size_t element_size);
int dynarray_get(DynamicArray *array, size_t index, void *destination);
int dynarray_set(DynamicArray *array, size_t index, void *element);
int dynarray_append(DynamicArray *array, void *element);
int dynarray_pop(DynamicArray *array);
size_t dynarray_len(DynamicArray *array);
void dynarray_free(DynamicArray *array);
```

```
struct DynamicArray {
    size_t element_size;  // size of each element in bytes
    size_t current_size;  // current number of elements in the array
    size_t capacity;      // current capacity (in number of elements) of the array
    void  *data;          // pointer to the array's data
                          //  (of size element_size * capacity)
};
```
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# Useful Functions

Read the man pages for usage information

* `malloc(3)`, `realloc(3)`, and `free(3)`
* `memcpy(3)` and `memmove(3)`

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# Get Started!