Sum of Digits Calculation

# Introduction

In this lab, we will learn to write a program to calculate the sum of digits of a given number in C programming language.

> 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