“Hello, World!” for C and C++

Here’s the classic “Hello, World!” code for both C and C++, along with explanations and how to compile/run them.

---

C Hello World

Code

#include <stdio.h> // Required for input/output functions like printf

int main() {
    // printf is a function used to print formatted output to the console
    printf("Hello, World!\n"); 
    
    // main returns an integer. 0 typically indicates successful execution.
    return 0; 
}

Explanation

• #include <stdio.h>: This line is a preprocessor directive. It tells the C compiler to include the contents of the stdio.h (Standard Input/Output) header file. This file contains declarations for standard I/O functions, including printf().
• int main() { ... }: This is the main function, which is the entry point of every C program.
  • int: Specifies that the main function will return an integer value.
  • main(): The name of the function.
  • { ... }: The curly braces define the body of the function, containing the statements to be executed.
• printf("Hello, World!\n");:
  • printf(): This is a standard library function used to print output to the console.
  • "Hello, World!\n": This is a string literal passed as an argument to printf(). It’s the text that will be displayed.
  • \n: This is an escape sequence that represents a “newline” character. It moves the cursor to the beginning of the next line after printing “Hello, World!”.
  • ;: Every statement in C must end with a semicolon.
• return 0;: This statement indicates that the main function has finished executing successfully. A return value of 0 is conventionally used to signify successful program termination.

How to Compile and Run (using GCC)

• Save: Save the code in a file named hello.c (or any name ending with .c).
• Compile: Open a terminal or command prompt and navigate to the directory where you saved the file. Then, run the following command:

  gcc hello.c -o hello 
  

  • gcc: The C compiler (GNU Compiler Collection).
  • hello.c: Your source code file.
  • -o hello: Specifies the name of the executable output file (you can choose any name, like myprogram).
• Run:

  ./hello
  

  You should see:

  Hello, World!
  

---

C++ Hello World

Code

#include <iostream> // Required for input/output streams like std::cout

int main() {
    // std::cout is an object used to print output to the console
    // << is the insertion operator, used to send data to the output stream
    std::cout << "Hello, World!" << std::endl; 
    
    // main returns an integer. 0 typically indicates successful execution.
    return 0;
}

Explanation

• #include <iostream>: This line includes the iostream (Input/Output Stream) header file, which provides the C++ standard library’s stream-based I/O functionalities, including std::cout and std::endl.
• int main() { ... }: Similar to C, this is the main function, the program’s entry point.
• std::cout << "Hello, World!" << std::endl;:
  • std::cout: This is the standard output stream object in C++. It’s used to send data to the console. std:: indicates that cout belongs to the std (standard) namespace.
  • <<: This is the stream insertion operator. It “inserts” the data on its right into the output stream on its left.
  • "Hello, World!": The string literal to be printed.
  • std::endl: This is a manipulator that inserts a newline character and then flushes the output buffer. (You could also use '\n' like in C: std::cout << "Hello, World!\n";. '\n' is generally more efficient as it doesn’t force a buffer flush, but for simple “Hello, World!”, the difference is negligible).
  • ;: Every statement in C++ must end with a semicolon.
• return 0;: Same as in C, indicates successful program termination.

How to Compile and Run (using G++)

• Save: Save the code in a file named hello.cpp (or any name ending with .cpp, .cc, or .cxx).
• Compile: Open a terminal or command prompt and navigate to the directory where you saved the file. Then, run the following command:

  g++ hello.cpp -o hello
  

  • g++: The C++ compiler (part of GCC).
  • hello.cpp: Your source code file.
  • -o hello: Specifies the name of the executable output file.
• Run:

  ./hello
  

  You should see:

  Hello, World!
  

---

Both C and C++ can achieve the same basic output, but they use different standard libraries and approaches for input/output. C++’s iostream is generally considered more type-safe and extensible for complex I/O operations.