Control Statements in C

 ...
 <statement 1> 
 while(<expression>)
 {
    <statement 2>
 }
 <statement 3> 
 ...

 ...
 <statement 1> 
 do
 {
    <statement 2>
 } while(<expression>); 
 <statement 3> 
 ...

 ...
 <statement 1>
 for(<expression1>; <expression2>; <expression3>) 
 { 
    <statement 2>
 }
 <statement 3> 
 ...

 #include <stdio.h> 
 main() 
 {
	int ntot, n=1; 
	float num, avg, sum=0; 
	printf("\nSpecify how many numbers you will feed: ");
	scanf("%d", &ntot);
 
	while(n <= ntot)
	{
		printf("Give Number %d: ",n);
		scanf("%f", &num);
		sum += num;
		n++;
	}

	avg = sum/ntot;
	printf("\nThe average is %f\n", avg);
 }

 #include <stdio.h> 
 main() 
 {
	int ntot, n=1; 
	float num, avg, sum=0; 
	printf("\nSpecify how many numbers you will feed: ");
	scanf("%d", &ntot);
 
	do
	{
		printf("Give Number %d: ",n);
		scanf("%f", &num);
		sum += num;
		n++;
	} while(n <= ntot);
  
	avg = sum/ntot;
	printf("\nThe average is %f\n", avg);
 }

 #include <stdio.h> 
 main() 
 {
	int ntot, n; 
	float num, avg, sum=0; 
	printf("\nSpecify how many numbers you will feed: ");
	scanf("%d", &ntot);
 
	for(n = 1; <= ntot; n++)
	{
		printf("Give Number %d: ",n);
		scanf("%f", &num);
		sum += num;
	}

	avg = sum/ntot;
	printf("\nThe average is %f\n", avg);
 }

 /* Program to check whether a given number is a palindrome or not */
 #include <stdio.h>
 main()
 {
	int number, digit, reverse=0, store_num;

	printf("Give a Number:");
	scanf("%d", &number); fflush(stdin);
	store_num = number;

	do
	{
		digit = number % 10;
		reverse = (reverse * 10) + digit;
		number /= 10;
	}while(number != 0);

	number = store_num;
	if(number == reverse)
		printf("The number is a palindrome.\n");
	else
		printf("The number is not a palindrome.\n");

    return;
 }

 for(i=1,j=2; i<5,j<10; ++i,j++)
 {
	...
 }

 /* begin loop1 */ 
 {
	<statement 1>;
	/* begin loop2 */
	{
		<statement 2>;
	} /* end of loop2 */
	<statement 3>;
 } /* end of loop1 */ 

 #include <stdio.h> 
 #define no_of_students 30 
 main() 
 {
   int no_of_courses_registered, grade, credit;
   int total_credits, course_no, i=1, j, sum; 
   float average_grade; 
   char student_name[61], subject[41]; 

   printf("Begin AVERAGE GRADE COMPUTATION for %d students\n", no_of_students);

   /* begining of the outer loop */ 
   while(i <= no_of_students) 
   {
      printf("\nEnter Name of student%d and number of courses registered by him: ",i); 
      scanf("%s %d",student_name,&no_of_courses_registered); fflush(stdin);
      sum = 0;
      total_credits = 0; 
      if(no_of_courses_registered == 0) 
      {
         printf("\nStudent %s has not registered in any course.\n", student_name); 
         i++;
         continue;
      }

      printf("Processing grades of student %s\n", student_name);

      /* begining of the inner loop */
      for(j=1; j <= no_of_courses_registered; j++) 
      {
         printf("\nEnter Course No., Subject, Credit & Grade in course %d: ", j); 
         scanf("%d %s %d %d", &course_no, subject_name, &credit, &grade); fflush(stdin);
         sum += credit * grade;
         total_credits += credit; 
      } /* end of the inner loop */ 

      average_grade = sum / total_credits; 
      printf("\nAverage grade obtained by %s is %f\n", student_name, average_grade); 
      i++; 
   } /* end of outer loop */ 
   printf("End of AVERAGE GRADE COMPUTATION.\n"); 
 }

 #include <stdio.h> 
 main() 
 {
	int a, b, sum;
	...
	...
	sum += (a + b);
	goto printf_statement;
	...
	...
	...
	printf_statement : printf("sum is %d\n", sum);
	...
	...
 }

(1) Enter compile and run the following program to understand the use of while 
    and for statement with pre and post decrement operators.

	(a)	#include <stdio.h>
		main()
		{
			int n= 0,a = 0;
			while (n)
			{
				a++;
				n--;
				printf("value of a is %d\n",a);
				a = 0; n = 10;
				a++;
				printf("value of a is %d\n",a);
			}
		}

	(b)	#include <stdio.h>
		main()
		{
			int n, i, k;
			printf("Enter a positive value\n");
			scanf("%d",&n);
			i = 10;
			k = 1;
			q = n/i;
			while(q != 0)
			{
				i = i * 10;
				k++;
				q = n/i;
			}
			printf("\n The no. of digits in %d is %d\n",n,k);
		}

	(c)	#include <stdio.h>
		main()
		{
			char ch;
			ch = 'A';
			while (ch <= 'Z')
			{
				putchar(ch);
				++ch;
			}
			putchar ('\n');
			ch = 'z';
			while (ch >= 'a');
			{
				putchar(ch);
				--ch;
			}
		}

	(d)	#include <stdio.h>
		main()
		{
			int  i, j, sum = 0, prod = 0, k = 0;
			for(i = 0; i <= 10; i ++)
				sum += i;
			printf("The sum up to 10 is %d\n",sum);
			for(i = 10; i == 0,j <= 10; i ==,  j++)
				prod = prod + i * j;
			printf("The producer is %d\n",prod);

			//Note that in for below expression1 & expression 2 are not there
			//Yet ; is there to tell the compiler that i!=0 is expression 2
			for(;i!=0;)
			{
				i = i/3;
				k++;
			}
			printf("This loop has executed %d times \n",k);
		}

	(e)	#include <stdio.h>
		main()
		{
			char ch;
			for(ch = 'A'; ch <= 'Z'; ++ch)
				putchar(ch);
			putchar('\n');
			for(ch = 'z'; ch>= 'a'; --ch)
				putchar(ch);
			putchar('\n');
		}


(2) Write a C program, which calculates the sum of every 5th integer starting with i=2,
    for all value of i that are less than 200.
    (Hint: Find the sum of 2 + 7 + 12 + 17 + ...)
    Write the iteration part,
	(a) using a while statement 
	(b) using a do-while statement
	(c) using a for statement

(3) Write a C program, which continuously accepts characters (within a loop) from the 
    user (max. 80 times), and displays the corresponding ASCII value.
    Implement the loop using while, do-while and for constructs.

(4) Consider a modification of the previous problem, in which the program should print:
     - how many characters read are letters,
     - how many are digits,
     - how many are whitespace characters, and
     - how many are of other types
    (Hint: make use of switch construct as well)

(5) Write a C program to construct a pyramid of digits.
    The user provides the depth of the pyramid.
    For example if the user inputs 5, the pyramid to be contructed is as follows:
             1
           2 3 2
          3 4 5 4 3
        4 5 6 7 6 5 4
      5 6 7 8 9 8 7 6 5

(6) Write a C program, which will print the maximum and the minimum numbers from
    a list of number entered by the user.

(7) The Fibonacci number are members of a sequence in which each number is equal
    to the sum of the previous two numbers in the series. Thus, fi = (fi-1) + (fi-2),
    where fi is the i-th Fibonacci number.
    Write a program that will print Fibonacci numbers up to 100. Note: fo = f1 = 1

(8) A natural number is called a prime number if it is perfectly divisible (i.e. has 
    no remainder when divided) only by 1 or by itself.
    Write a program to display the first 50 prime numbers. 

(9) For each student in a class, the following data is to be entered:
	roll no		integer
	name		string
	course		string
	attendence_record	float
	fees cleared	char ('y' to indicate yes, 'n' to indicate no)

    A student is allowed to appear in the final examination if he/she has cleared 
    the fees and has more than 80% attendance.

    Write a C program to accept student information from the user and print 
    the Name and Roll number of the students who can attend the examination.

    The program should halt when the user indicates no further input.