Before we study the basic building blocks of the C programming language, let us look at a bare minimum C program structure so that we can take it as a reference in the upcoming chapters.
Hello World Example
A C program basically consists of the following parts −
- Preprocessor Commands
- Functions
- Variables
- Statements & Expressions
- Comments
Let us look at a simple code that would print the words "Hello World" −
#include <stdio.h>
int main() {
/* my first program in C */
printf("Hello, World! \n");
return 0;
}
Let us take a look at the various parts of the above program −
- The first line of the program #include <stdio.h> is a preprocessor command, which tells a C compiler to include stdio.h file before going to actual compilation.
- The next line int main() is the main function where the program execution begins.
- The next line /*...*/ will be ignored by the compiler and it has been put to add additional comments in the program. So such lines are called comments in the program.
- The next line printf(...) is another function available in C which causes the message "Hello, World!" to be displayed on the screen.
- The next line return 0; terminates the main() function and returns the value 0.
Compile and Execute C Program
Let us see how to save the source code in a file, and how to compile and run it. Following are the simple steps −
- Open a text editor and add the above-mentioned code.
- Save the file as hello.c
- Open a command prompt and go to the directory where you have saved the file.
- Type gcc hello.c and press enter to compile your code.
- If there are no errors in your code, the command prompt will take you to the next line and would generate a.out executable file.
- Now, type a.out to execute your program.
- You will see the output "Hello World" printed on the screen.
$ gcc hello.c $ ./a.out Hello, World!
Make sure the gcc compiler is in your path and that you are running it in the directory containing the source file hello.c.
