Sum of Digits Using Recursion

# Introduction

Recursion is a programming technique where a function calls itself, allowing the function to repeat until a base case is met and the function returns the final output. In this lab, we will learn how to find the sum of digits of a given number using recursion.

> Note: You need to create the file `~/project/main.c` yourself to practice coding and learn how to compile and run it using gcc.

cd ~/project
# create main.c
touch main.c
# compile main.c
gcc main.c -o main
# run main
./main