Print "Hello World" in C/C++ without using any header file Last Updated : 13 Sep, 2023 Comments Improve Suggest changes Like Article Like Report Write a C/C++ program that prints Hello World without including any header file. Conceptually it's seems impractical to write a C/C++ program that print Hello World without using a header file of "stdio.h". Since the declaration of printf() function contains in the "stdio.h" header file. But we can easily achieve this by taking the advantage of C pre-processor directives. The fact is at the time of compiling a program, the first phase of C preprocessing expands all header files into a single file and after that compiler itself compiles the expanded file. Therefore we just need to extract the declaration of printf() function from header file and use it in our main program like that:- C language: Just declare the printf() function taken from "stdio.h" header file. C //Declare the printf() function int printf(const char *format, ...); int main() { printf( "Hello World" ); return 0; } Output: Hello World C++ language: We can't directly put the declaration of printf() function as in previous case due to the problem of Name mangling in C++. See this to know more about Name mangling. Therefore we just need to declare the printf() inside extern keyword like that:- CPP //Declare the printf() function inside //extern "C" for C++ compiler extern "C" { int printf(const char *format, ...); } int main() { printf( "Hello World" ); return 0; } Output: Hello World See this to know more about all phases of compilation of C program. This blog is contributed by Shubham Bansal. Comment More infoAdvertise with us Next Article Print "Hello World" in C/C++ without using any header file K kartik Follow Improve Article Tags : Misc C Language C++ c-puzzle Practice Tags : CPPMisc Similar Reads Print Hello World without semicolon in C/C++ Every statement in C++ must end with a semicolon as per basics. However, unlike other languages, almost all statements in C++ can be treated as expressions. However there are few scenarios when we can write a running program without semicolon. If we place the statement inside an if/switch/while/macr 2 min read How to write your own header file in C? As we all know that files with .h extension are called header files in C. These header files generally contain function declarations which we can be used in our main C program, like for e.g. there is need to include stdio.h in our C program to use function printf() in the program. So the question ar 4 min read Print "Hello World" with empty or blank main in C++ Write a program in C++ that prints "Hello World", it has a main function and body of main function is empty. Following are three different solutions. We can create a global variable and assign it return value of printf() that prints "Hello World" CPP // C++ program to print something with empty main 2 min read How to write a running C code without main()? Write a C language code that prints GeeksforGeeks without any main function. Logically it's seems impossible to write a C program without using a main() function. Since every program must have a main() function because:- It's an entry point of every C/C++ program.All Predefined and User-defined Func 2 min read Write a C program to print "Geeks for Geeks" without using a semicolon First of all we have to understand how printf() function works. Prototype of printf() function is: int printf( const char *format , ...) Parameter format: This is a string that contains a text to be written to stdout.Additional arguments: ... (Three dots are called ellipses) which indicates the vari 2 min read Like