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Let’s start making a simple program.
1) # Write a program to print a message?
#include<stdio.h>
#include<conio.h>
void main()
{
clrscr():
printf(“Hello. n How are you?”);
getch();
}
 First, compile program  press alt+F9. Now if no errors or warnings are found press
ctrl+F9 to run program.
 Here, stdio.h and conio.h are header files. Which contain pre-defined functions we use in
program.
 printf() is defined in stdio.h (standard input output header file).
clrscr() and getch() are defined in conio.h (console input output header file).
 printf() function allow to print set of characters written inside “”.
 clrscr() function clears output screen so that, previous outputs does not get mix with your
current output.
 getch() function holds output screen until any key is pressed to return from output
screen.
 Each program contains a main() function.
 Void is used as return type of main function. It is used with those functions which do not
return any value.
 Semi-colon (;) is used at end of every statement to terminate.
 { This represents opening of a block.
 }  This represents end of a block.
 Each block which opens must end.
 n  it is an escape sequence. We will discuss it latter in this chapter.
Output of the above program will be as:
Hello
How are you?

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2) # Write a program to enter a number and print it?
#include<stdio.h>
#include<conio.h>
void main()
{
int i;
clrscr();
printf(“enter a number”);
scanf(“%d”,&i);
printf(“n you have entered=%d”, i);
getch();
}
 int represents a data type, and I is a variable of integer type.
 %d is a format specifier. It tell which type of data scanf has to read from keyboard and
printf has to print on output screen. Here it is integer type.
 &  address of operator is used in scanf. It tells compiler, address of concerned variable
where input from keyboard has to be saved.
 An, important thing you should remember while writing any program is that, variable
should be declared always first then, write other lines of code.
For ex:
If in the above program you write it as;
Void main()
{
clrscr();
int i;
printf(“enter a number”);
scanf(“%d”,&i);
printf(“n you have entered=%d”, i);
getch();
}
As, first clrscr() is written then, variable I is declared therefore it will not work. It will give
an error “declaration is not allowed here.”

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