Basic Structure of a C program

In this section we will try to understand basic structure of a simple C program.

Let’s consider we don’t know anything about C programming if we know already. So we have no idea about its syntax or anything. Before introducing the basic terminology i would like to show you the basic C code first.

Let’s look at the code below. It is a simple C program.

#include <stdio.h>
int main()
{
    return 0;
}

So what this code means? Does it print anything? NO, it’s not going to print anything because we didn’t use any command which can print.

Wait a minute! Let’s add another line to our previous code before going to the first question.

#include <stdio.h>
int main()
{
    printf(“Hello World”);
    return 0;
}

OUTPUT :

Let’s try to understand the above program line by line.

^#include is a preprocessor command and <stdio.h> is a header. By including this, we get the access of using standard input/output form the C library before executing the code.

This line tells the compiler that there is a function called main, and this function returns an integer. Every C program must have exactly one main function. From the main function or this line, every C program starts execution.

Opening curly brace ^{ indicates the beginning of all functions in C. In this case it is indicating the beginning of the main function.

This whole line is a statement and ^{printf(“ ”)} is a function which prints the output on the screen. Whatever you write inside the quotes ^“” it will show that on screen after executing the program. What about the semicolon? It indicates the end of the statement. In C programming you have to put a semicolon after every statement.

It indicates the ^END of the program. We return a value from main to the operating system (we discussed before that main function returns an integer). A return value 0 means your program executed successfully.

Closing curly brace ^} indicates the end of the function.

Challenge :

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