Chapter 3
C Program Structure
Let’s look into Hello World example using C Programming Language
.
Before we study basic building blocks of the C programming language,
let us look a
bare minimum C program structure so that we can take it as a reference in upcoming
chapters
.
C 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
int main()
{
/* my first program in C */
printf("Hello, World! \n");
return 0;
}
Let us look various parts of the above program
1. The first line of the program #include
is a preprocessor command, which tells
a C compiler to include stdio.h file before going to actual compilation.
2. The next line int main() is the main function where program execution begins.
3. 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.
4. The next line printf(...) is another function available in C which causes the message
"Hello, World!" to be displayed on the screen.
5. The next line return 0; terminates main()function and returns the value 0.
Compile & Execute C Program
Let’s look at how to save the source code in a file, and how to compile and run it.
Following
are the simple steps:
1. Open a text editor and add the above-mentioned code.
2. Save the file as hello.c
3. Open a command prompt and go to the directory where you saved the file.
4. Type gcc hello.c and press enter to compile your code.
5. 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.
6. Now, type a.out to execute your program.
7. You will be able to see "Hello World" printed on the screen
$ gcc hello.c
$ ./a.out
Hello, World!
Make sure that gcc compiler is in your path and that you are running it in the directory
containing source file hello.c.
Friday, May 22, 2015
