Hello World

#include <stdio.h>

int main(void)
{
  printf("Hello, world!\n"); // Output: Hello, world!
  return 0;
}

Let’s break this down:

1. #include <stdio.h>: This preprocessor directive tells the compiler to include the program’s standard input/output library. The library contains functions the program will use for input/output operations - in this case, printf.
2. int main(void): This is the program’s main function. Every C program must have a main function as this is where program execution begins. The int before main signifies that the function will return an integer. The (void) is an optional part that signifies that the function takes no arguments.
3. {...}: The pair of curly braces denotes a block of code associated with a function. In this case, it contains the body of the main function. All the code that the main function executes is placed within these braces.
4. printf("Hello, world!\\n");: This is a call to the printf function, defined in stdio.h. printf is used to output text to the console. The argument provided, "Hello, world!\\n", is a string to be printed. The \\n at the end is an escape sequence representing a newline character, causing the cursor to go to the next line after printing the text.
5. // Output: Hello, world!: This is a single-line comment. In C, any text that comes after // on the same line is considered a comment and is ignored by the compiler. Comments are used to provide information about the code to human readers. In this case, it explains what the output of the printf statement will be.
6. return 0;: This line signifies the end of the main function. The return keyword is followed by an integer value that signifies the program’s exit status. A return value of 0 typically signifies that the program has been executed successfully. Different non-zero return values can indicate different types of errors, which can be helpful for debugging.
7. }: This is the closing brace for the main function. It signifies the end of the function’s code block.

This program is a simple “Hello, World!” program and is often used as an introductory example for people learning the C language. When executed, it simply prints “Hello, World!” and a newline to the console and then exits with a status of 0.