chapter04

Chapter 4- Loop Control Instructions

What is Loop?

Loops are used to repeat one or more statements for a given condition.
The versitality of computer lies in it's abiility to perform a set of instruction repeatly. This involve repeating some question of program either specify no. of time vertical.
This repeative operator is done through loop control statement.

loops are used to repeat similar part of a code snippet efficiently

Three conditions of loop

• Initialization
• Condition
• Increment/decrement

1. Print 1 to 100 numbers one by one

Types of loops

• While Loop
• Do while loop
• For loop

while loop

while (/* condition is true*/)
    {
        /* code */    ---the block keeps executing as long as the condition true
    }

2. Example of while loop

If the condition never becomes false, the while loop keeps getting executed, such a loop is known as infinite loop

3. write a program to print natural numbers from 10 to 20 when initial loop counter is initialized to 0

4. write a program to calculate simple interest for 3 sets of p,n and r.

The loop counter not need to be int, it can be float as well

Incement and decrement operators

i++ ----  i is increased by 1(i+1)
i--      ---- i is decreased by 1

5. See an example of increment and decrement operators

i++ means first print value then increment
++i means first incement then print value

Post-Increment (i++)

The i++ method, or post-increment, is the most common way. In psuedocode, the post-increment operator looks roughly as follows for a variable i:

int j = i;
i = i + 1;
return j;

Since the post-increment operator has to return the original value of i, and not the incremented value i + 1, it has to store the old version of i.

Pre-Increment (++i)

The ++i method, or pre-increment, is much less common and is typically used by older programmers in languages such as C and C++.

i = i + 1;
return i;

Important

• +++ operator does not exist
• += is compound assignment operator
  just like -=,+=,/=
  

  if i=5, i+=10 --> Incements i by 10-->15

Do-While Loop

very similar to while loop
While loop which executes at least once
syntax

do
    {
        /* code */
    } while (/* condition */);

While

Checks the condition and then executes the code.

Do while

Executes the code and then checks the condition.

6. Program on do while loop.

7. Write a program to print first n natural numbers using do-while loop.

For Loop

Syntax

for (initialize ; test ; increment or decrement)
    {
        /* code */
    }

8. Write a program to print zero to 10 numbers using for loop.

Initialize

Setting a loop counter to an initial value.

Test

Checking a condition.

Increment

Updating the loop counter.

9. example of using for loop.

10. Write a program to print first n numbers using for loop.

11. Decrementing for loop.

12. write a program to print n natural numbers in reverse order.

13. Write a program to print the table of any number

Break Statement

The break statement is used to exit the loop irrespective of whether the condition is true or false. whenever a "break" is encountered inside the loop, the control is sent outside the loop.
Using break statement

for (int i = 0; i < 1000; i++)
    {
        printf("%d\n",i);
        if (i==5)
        {
            break;
        }
        
    }

14. Using break statement inside a do while loop

Continue statement

Continue statement is used to immidiately move to the next iteration of the loop.
The control is taken to the next iteration thus skipping everything below "continue" inside the loop for that iteration.

int s =5;
    int i=0;
    while (i<10){
        if(i!=s){
            continue;
        }
        else
        {
            printf("%d",i);
            i++;
        }
    }

15. Using continue statement

Exercises

1. Write a program to print a multiplication table of a given number.
   
2. Write a program to print multiplication table of 10 in reverse order
   
3. Write a program to sum first 10 natural numbers.
   

   a. Using For loop
   b. Using While loop
   c. Using Do while loop

4. Write a program to calculate the sum of the numbers occuring in the multiplication table of 8.(Consider 8x1 to 8x10)

5. Write a program to calculate the factorial of a given number using a for loop 6. Repeat 8 using while loop 7. Write a program to check whether a given number is prime or not using loops
8. Implement 7 question with other loops

a. using while loop
b.Using do while loop 

9. Write a program to reverse any number
10. Write a program to add all digits of a given number
11. Write a program to sort all even and odd numbers