C LANGUAGE INTRODUCTION

The only way to learn a new programming language is by writing programs in it. The first program to write is the same for all languages:
Print the words:hello, world

In C, the program to print ``hello, world'' is
#include
main()
{
printf("hello, world\n");
}
Just how to run this program depends on the system you are using. 
complie the program click the alt+F9.and dispaly errors and warning.errors and warnings must be zero and next run the program click ctrl+F9 to display the output
As a specific example, on the UNIX operating system you must create the program in a file whose name ends in ``.c'', such as hello.c, then compile it with
the command
cc hello.c
If you haven't botched anything, such as omitting a character or misspelling something, the compilation will
proceed silently, and make an executable file called a.out. If you run a.out by typing the command
a.out
it will print
hello, world
ANOTHER EXAMPLE:

An example of simple program in C

#include

int main(void)

{

          printf(“HAI HOW ARE YOU\n”);

          printf(“FINE ”);

          printf(“you know the trick\n”);

          return(0);

} 

 

The previous program will produce the following output on your screen 

 HAI HOW ARE YOU

 FINE you know the trick

 

a C program line begins with # provides an instruction to the C preprocessor

It is executed before the actual compilation is done.

Two most common directives :

#include

#define 

In our example (#include) identifies the header file for standard input and output needed by the printf().

 

Identify the start of the program

Every C program has a main ( )

'main' is a C keyword.  We must not use it for any other variable

 

Identify a segment / body of a program

The start and end of a function

The start and end of the selection or repetition block.

Since the opening brace indicates the start of a segment with the closing brace indicating the end of a segment, there must be just as many opening braces as closing braces  (this is a common mistake of beginners) 

 

Each statement in C needs to be terminated with semicolon (;) 

Each statement in C needs to be terminated with semicolon (;)