Lesson 02·C Programming
Structure of Program
The standard layout and organization of a C program
The Basic Structure of C Program
Structure Outline
/* [ Document Section ] */
/* [ Links Section ] */
/* [ Definition Section ] */
/* [ Global declaration section ] */
void main() {
/* [ Variable declaration section ] */
/* [ Function declaration section ] */
/* [ Executable statements ] */
}
/* function definition 1 */
void func1() {
/* --------------------- */
/* --------------------- */
}
/* function definition 2 */
void func2() {
/* --------------------- */
/* --------------------- */
}Explanation of Program Sections
- Document Section: Contains set of comment lines giving name of the program, author, and details.
- Links Section: Provides instructions to the compiler to link functions from system libraries (e.g., #include <stdio.h>).
- Definition Section: Defines all symbolic constants using preprocessor directives (e.g., #define PI 3.14).
- Global Declaration Section: Declares variables and user-defined functions that are accessible across the entire program.
- main() Function: The mandatory entry point of execution for every C program containing declaration and executable parts.
- Subprogram Section: Contains user-defined functions called by main() or other subprograms.
Example Program: Fibonacci Series
A complete practical program demonstrating the basic structural sections in action:
C Example
#include <stdio.h>
int main()
{
int n1 = 0, n2 = 1, n3, i, number;
printf("Enter the number of elements: ");
scanf("%d", &number);
printf("\n%d %d ", n1, n2); // printing 0 and 1
/* for loop starts from 2 because 0 and 1 are already printed */
for (i = 2; i < number; ++i)
{
n3 = n1 + n2;
printf("%d ", n3);
n1 = n2;
n2 = n3;
}
return 0;
}Program Output
Enter the number of elements: 8 0 1 1 2 3 5 8 13