ANSWER :

1.1 ITERATION

Iteration is a processing repeating some task. In a real time programming, we require a set of statements to be repeated certain number of times and/or till a condition is met. Every programming language provides certain constructs to achieve the repetition of tasks. Most used Iterator are While & for.

1.1.1 The while Statement

The while loop has the syntax as below -

Here,

while

is a keyword. The condition is evaluated first. Till its value remains true, the statement_1 to statement_n will be executed. When the condition becomes false, the loop is terminated and statements after the loop will be executed. Consider an example -

1.1.2 While Structure:

When a while loop is executed, expr is first evaluated in a Boolean context and if it is true, the loop body is executed. Then the expr is checked again, if it is still true then the body is executed again and this continues until the expression becomes false.

1.1.3 Example - 1:

Fig 1.3 Program of while

Fig 1.4: Output of Fig 1.3

In the above example, a variable n is initialized to 1. Then the condition n<=5 is being checked. As the condition is true, the block of code containing print statement (print(n)) and increment statement (n=n+1) are executed. After these two lines, condition is checked again. The procedure continues till condition becomes false, that is when n becomes 6. Now, the while-loop is terminated and next statement after the loop will be executed. Thus, in this example, the loop is

iterated

for 5 times.

Note that, a variable n is initialized before starting the loop and it is incremented inside the loop. Such a variable that changes its value for every iteration and controls the total execution of the loop is called as

iteration variable

or

counter variable

. If the count variable is not updated properly within the loop, then the loop may not terminate and keeps executing infinitely.

1.1.4 Single statement while block

Just like the if block, if the while block consists of a single statement the we can declare the entire loop in a single line. If there are multiple statements in the block that makes up the loop body, they can be separated by semicolons (;).

Fig 1.5 Program to demonstrate Single Statement while Block

Fig 1.6: Output of Fig 1.5

1.1.5 The break Statement

With the

break

statement we can stop the loop even if the while condition is true:

Fig 1.7: Break in while Statement

Fig 1.8: Output for Fig 1.7

1.1.6 The continue Statement:

With the continue statement we can stop the current iteration, and continue with the next:

Fig 1.9: Continue in While Loop

Fig 1.10: Output of Fig 1.9

1.1.7 The else Statement

With the else statement we can run a block of code once when the condition no longer is true:

Fig 1.11: Use of Else in while statement

Fig 1.12: Output of Fig 1.11

ANSWER :

Fig 2.1: Program to demonstrate Counting Summing & Average using Looping Statement - for loop

Fig 2.2: Output of Fig 2.1

ANSWER :

3.1 String:

A string is a sequence of characters. You can access the characters one at a time with the bracket operator:

>>>

fruit = 'banana'

>>>

letter = fruit[1]

The second statement extracts the character at index position 1 from the fruit variable and assigns it to the letter variable. The expression in brackets is called an index. The index indicates which character in the sequence you want (hence the name).

3.2 Traversal of String using with a loop:

3.2.1 Using For Loop:

Fig 3.1: Traversal using for loop

3.2.2 Using while loop:

Fig 3.3: Traversal using While Statement

Fig 3.4: Output of Fig 3.3

ANSWER :

4.1 While loop:

Refer 1^st Question & Answer or Click Here

4.2 for loop:

The while loop iterates till the condition is met and hence, the number of iterations are usually unknown prior to the loop. Hence, it is sometimes called as indefinite loop. When we know total number of times the set of statements to be executed,

for

loop will be used. This is called as a

definite loop.

The for-loop iterates over a set of numbers, a set of words, lines in a file etc. The syntax of for-loop would be -

Here,

for

and

in

are keywords

List/sequence

is a set of elements on which the loop is iterated. That is, the loop will be executed till there is an element in list/sequence

Statements

constitutes body of the loop

4.2.1 Example:

Fig 4.2 Demonstrating for looping Statement

Fig 4.3: Output for Fig 4.2

4.2.2 Looping through a String:

Refer 3^rd Question & Answer.

4.2.3 The break Statement: (same as in While Loop)

With the break statement we can stop the loop before it has looped through all the items:

Fig 4.4: Break Statement in For Loop

Fig 4.5: Output of Fig 4.4

4.2.4 The continue Statement: (same as in While Loop)

With the continue statement we can stop the current iteration of the loop, and continue with the next:

Fig 4.6: Continue Statement in for loop

Fig 4.7: Output for Fig 4.6

4.2.5 The range( ) Function:

To loop through a set of code a specified number of times, we can use the range( ) function,

The range( ) function returns a sequence of numbers, starting from 0 by default, and increments by 1 (by default), and ends at a specified number.

range(init value, ending number, increment value)

Fig 4.8: range function Demonstartion

Fig 4.9: Output of Fig 4.8

4.2.6 Nested Loops:

A nested loop is a loop inside a loop.

The "inner loop" will be executed one time for each iteration of the "outer loop":

Fig 4.10: Nested For loop statement

Fig 4.11: Output for Fig 4.10

4.2.7 The pass Statement

for loops cannot be empty, but if you for some reason have a for loop with no content, put in the pass statement to avoid getting an error.

Fig 4.12: Error Because There is no Body in for loop

Fig 4.13: Use of pass keyword in for loop for empty body

Fig 4.14: Output for Fig 4.13

ANSWER :

Fig 5.1 Program to compare String & concatenate if both strings are not same.

Fig 5.2: Output for Fig 5.1