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Lab 3 – Arrays, Pointers, and Strings

In this lab you will practice three core topics in C programming:

  1. Array processing (min, max, sum, average)
  2. Pointers as function parameters (swap, modify)
  3. Manual string handling (strlen, strcpy)

You will work on three separate C source files:

  • lab3_task1.c
  • lab3_task2.c
  • lab3_task3.c

Each file already contains:

  • A comment header with your Name and Student ID to fill in
  • Function prototypes
  • A simple main with example tests
  • Placeholders (// TODO) where you need to write code

Acquiring Lab 3 Files in Codespaces

There are two ways to get the new Lab 3 files into your Codespaces.
Choose the method that fits your situation.

Option A – Update Your Existing Codespace (Recommended)

If you already forked the course repository in Week 1 and created a Codespace, you can simply pull the new files.

  1. Open your existing Codespace.
  2. Make sure you are on the main branch from terminal: 
    git checkout main
  3. Check that you have the teacher’s repository set as upstream: git remote -v You should see something like this in the output:
origin    https://github.com/student123/RTU_Programming_Languages_C_Lab_Fall_2025.git (fetch)
upstream  https://github.com/ValRCS/RTU_Programming_Languages_C_Lab_Fall_2025.git (fetch)

If you do not see upstream, add it manually: git remote add upstream https://github.com/ValRCS/RTU_Programming_Languages_C_Lab_Fall_2025.git 4. Pull the new files from the teacher repository: git pull upstream main 5. After this, you should see the new files:

src/lab3_task1.c
src/lab3_task2.c
src/lab3_task3.c
week3_instructions.md

Option A2 – Update Your Fork Using GitHub "Sync Fork" Button

If you don’t want to use terminal commands in Codespaces, you can update your fork directly on the GitHub website.

Steps

  1. Open your fork of the course repository on GitHub (e.g. https://github.com/student123/RTU_Programming_Languages_C_Lab_Fall_2025).
  2. On the repository page, you should see a “Sync fork” button near the top of the page.
    • If your fork is behind the teacher’s repository, GitHub will show something like:
      “This branch is 3 commits behind ValRCS:main”.
  3. Click the “Sync fork” button, then click “Update branch” to bring your fork up to date.
  4. After that, go back to your Codespace and run:
   git pull origin main

This will download the updated files from your fork into your Codespace. ⚠️ Note: The “Sync fork” method updates your fork on GitHub, but you still need to run git pull origin main inside your Codespace to get the new files locall

Option B – Create a New Fork and Codespace (Only if Needed)

Use this option only if:

  • You accidentally deleted your Codespace, or
  • Your fork is broken and cannot be updated.

Steps:

  1. Go to the teacher repository.
  2. Click Fork to create your own copy under your GitHub account.
  3. When forking, GitHub may ask for a repository name.
    • Example: if your GitHub username is student123, the default fork name will be
      student123/RTU_Programming_Languages_C_Lab_Fall_2025.
    • If you already created a fork in Week 1 or Week 2, you will need to rename this new fork (e.g. RTU_Programming_Languages_C_Lab_Fall_2025_v2) to avoid conflicts.
  4. Open the newly forked repository in GitHub and click:
    Code → Codespaces → Create Codespace on main
  5. You will now have a fresh Codespace with all files, including Lab 3. NOTE: Option A is much preferred. At some point in your future jobs you will not be allowed to just fork anytime you need a fresh copy - that is highly unprofessional.

Task 1 – Array Algorithms (lab3_task1.c)

Implement the following functions for integer arrays:

  • int array_min(int arr[], int size) – return the smallest element
  • int array_max(int arr[], int size) – return the largest element
  • int array_sum(int arr[], int size) – return the sum of elements
  • float array_avg(int arr[], int size) – return the average as a float

Rules:

  • Do not use external libraries besides <stdio.h>.
  • Write separate functions for each operation.

Example:

int arr[] = {10, 20, 5, 30, 15};
printf("Min: %d\n", array_min(arr, 5));  // 5
printf("Max: %d\n", array_max(arr, 5));  // 30
printf("Sum: %d\n", array_sum(arr, 5));  // 80
printf("Avg: %.2f\n", array_avg(arr, 5));// 16.00

Task 2 – Pointers in Function Parameters (lab3_task2.c)

Practice using pointers to modify values inside functions.

Implement

  • void swap(int *x, int *y) – swap the values of two integers
  • void modify_value(int *x) – multiply the value by 2

Rules

  • Functions must modify the caller’s variables via pointers.
  • Test your functions in main.

Example

int a = 3, b = 7;
printf("Before swap: a=%d, b=%d\n", a, b);

swap(&a, &b);
printf("After swap: a=%d, b=%d\n", a, b);

modify_value(&a);
printf("After modify_value: a=%d\n", a);

Task 3 – String Handling (lab3_task3.c)

Write your own versions of two basic string functions:

Implement

  • int my_strlen(const char *str) – return the number of characters (not counting '\0')
  • void my_strcpy(char *dest, const char *src) – copy a string into dest

Rules

  • Do not use <string.h> functions.
  • Use loops or pointer arithmetic.
  • Ensure dest has enough space to hold the copied string.

Example

char text[] = "hello";
int len = my_strlen(text);       // 5

char buffer[100];
my_strcpy(buffer, text);
printf("%s\n", buffer);          // hello

Submit

  • As usual, for each assignment submit the source code file for the assignment lab3_task1.c for first and so on.
  • Alternatively, you can also submit the link to your repository which has this MODIFIED BY YOU file. Not just my original stub..