Structure of a C Program

 #include <stdio.h> /* a preprocessor directive to include the file stdio.h */
 #include <math.h>
 /* program to find the real roots of a quadratic polynomial */

 main()
 {
	/* type declaration of the variable */
	float a, b, c, discriminant, d, w, root1, root2;  /* function declaration */
	float compute_discriminant(float x, float y, float z);

	printf("Give the values of the coefficients a,b,c of the polynomial:");
	scanf("%f,%f,%f", &a, &b, &c);

	fflush(stdin); /* flushing the buffer associated with standard input */
	discriminant = compute_discriminant(a,b,c);  /* invoking a function */
	d = 2 * a;
	if(discriminant == 0)
		printf("The roots are equal %f\n", - b / d);
	else
		if(discriminant < 0)
			printf("The roots are complex\n");
		else
		{
			w = sqrt(discriminant);
			printf("The roots are real and different\n");
			root1 = (-b - w) / d;
			root2 = (-b + w) / d;
			printf("Root1 = %f, Root2 = %f\n",root1,root2);
		}
    return;
 }


 /* Function definition */
 float compute_discriminant (float x, float y, float z)
 {
	float d;                 /* local variable declaration */
	d = y * y - 4 * x * z;
	return d;
 }

1. Identify the errors in the following C program:

	# include { STDIO.H }*/ c program *\
	main [ ]{  printf("Welcome to C"} ;
	
	Correct the program to display "Welcome to C" on the screen.


2. Match the following:

	(i)   main			(a) defined in the header file stdio.h
	(ii)  /*.. */			(b) terminates a expression
	(iii) ;				(c) encloses compound statements
	(iv)  { }			(d) the controlling function of a C program
	(v)   printf			(e) encloses comment entries


3. Do you find anything odd in the following program?

	# include <stdio.h>
	main()
	{  /*
		printf("Hi! How are you !!!!");
	*/ 
	}


4. In the function, xyz (a, b, c); a, b and c are known as_____________.


5. LAB WORK: Enter, compile and run the following c program and watch their output. Note that some of 
   the programs contain typical errors which are done by beginner programmers. So, study the errors 
   carefully and correct the programs.

	a)	# include<stdio.h>
		main()
		{
			printf("Welcome to c programming\n"); 
			printf("Hope you enjoy programming\n");
			printf("Wish you a good beginning\n\n");
		}

		
	b)	# include <stdio.h.
		main()
		{
			char name [30];
			printf("This program demonstrates how C interacts with an user\n");
			printf("Enter your name:");
			gets(name);
			fflush(stdin);
			printf("Your name is : %s\n",name);
		}


	c)	# include <stdio.h>
		main()
		{
			/* C does quick calculate for you */
			/* Multiplication and division */
			int num1,num2,result=0;

			printf("\nEnter the first number:");
			scanf("%d",&num1);
			fflush(stdin);

			printf("\nEnter the second number:");
			scanf("%d",&num2);
			fflush(stdin);

			/* multiplication */
			result = num1* num2;
			printf("We get %d after dividing %d by %d\n",result, num1,num2);

			/* Division */
			result = num1 / num2;
			printf("We get %d after dividing %d by %d\n",result, num1,num2);
		}


	d.	# include <stdio.h>
		/* This is a demonstration of modular programming */
		main() /* controlling module */
		{
			printf("We are in main function now…\n");
			message();
			printf(We are back in function main again…\n");
		}
		message()
		{
			printf("Hi! We are in message now and returning to main\n");
		}