C LAN

2. Structure of a C program

4. 1.Documentation section-suggest
2.Preprocessor section/link/header
file-mandatory
3.Definition section-optional
4.Global declaration-optional
5.Main function-mandatory
6.User defined functions/sub
program-optional

5. Documentation section
• It includes the statement specified at the
beginning of a program, such as a
program's name, date, description, and title. It is
represented as:
ex: //name of a program
• Or
• /*
• Overview of the code
• .
• */

6. Preprocessor section
• The preprocessor section contains all the
header files used in a program. It informs the
system to link the header files to the system
libraries. It is given by:
• #include<stdio.h> Standard Input Output
• #include<conio.h> console input output
library functions
• # include <math.h>mathematic functions

7. Functions
• Built-in and user define
• Built in – printf()-o/p function
scanf()-i/p

8. Define section
• The define section comprises of different
constants declared using the define keyword.
It is given by: symbolic const..
• #define a = 2
• #define PI=3.14

9. Global declaration
• The global section comprises of all the global
declarations in the program. It is given by:
• Variables two types
• Local and global
Ex: main()
{
Int a=10; local
}

10. Ex: Int x = 30
main()
{
} Global
{
}

11. Main function
main() is the first function to be executed by the
computer. It is necessary for a code to include
the main().
Ex: main()
{
Declaration part
Executable part
}

12. • Ex: main()
• {
• Int a,b,c;
• a=10;
• b=20;
• C=a+b
• }

13. User defined
functions or sub programs-optional
• The user defined functions specified the
functions specified as per the requirements of
the user. For example, color(), sum(),
division(), etc.

14. Sample program
• /* Sum of two numbers */ documentations sec..
• #include<stdio.h> link sec..
• int main() global declaration function
• {
• int a, b, sum; local variable section
• printf("Enter two numbers to be added "); Declaration part
• scanf("%d %d", &a, &b);
• sum = a + b; executable part
• printf("%d + %d = %d", a, b, sum);
•
• }

15. • Output