Introduction to programming – Lecture 4: iteration statements (loops)

1. Introduction to programming – Lecture 4: iteration statements (loops)

INTRODUCTION TO PROGRAMMING –
LECTURE 4: ITERATION STATEMENTS (LOOPS)
Aigerim Aibatbek - Senior Lecturer
aigerim.aibatbek@astanait.edu.kz

2. Iteration Statement

ITERATION STATEMENT
Suppose that you need to display a message "Welcome to C++!” 100 times.
100 times
100 times
…
…
It would be tedious to write the above statements 100 times! So, how do you solve the problem?

3. Iteration Statement

ITERATION STATEMENT
Use Iteration statements (loops)!
The statement which forces another statement or a
group of statements to be executed repeatedly
Loops can execute a block of code as long as a
specified condition is reached.
Entry
Check the condition
If false -Exit

4. loops

LOOPS
Loop types
For loop
While loop
Do while
loop

5. The For Loop

THE FOR LOOP
Syntax:
Update counter
for (statement 1; statement 2; statement 3) {
// code block to be executed
}
Statement 1(Initialization): is executed (one time) before the
execution of the code block.
Statement 2 (Condition): defines the condition for executing the
code block.
Statement 3 (Incrementation): is executed (every time) after the
code block has been executed (the last action at each iteration)
The for-loop flow chart

6. The For Loop

THE FOR LOOP
Suppose that you need to display a message "Welcome to C++!” 100 times.
100 times
…

7. The For Loop

THE FOR LOOP
Some more examples:
Output:
Output:
Output:

8. The While Loop

THE WHILE LOOP
Syntax:
while (condition) {
// code block to be executed
}
Update counter
The most straightforward looping structure
Any control variable manipulations are made inside of the
loop`s body
Initializations of control variables must be outside of the loop
The while-loop flow chart

9. The While Loop

THE WHILE LOOP
1. Display message "Welcome to C++!” 100 times.
3. Display numbers in reversed order
2. Display counter values
4. Display the odd numbers between 1 and 10

10. The Do-While Loop

THE DO-WHILE LOOP
Syntax:
do {
// code block to be executed
}
while (condition);
True
This loop will execute the code block first (at least once), before
checking if the condition is true
Then it will repeat the loop as long as the condition is true.
false
Any control variable manipulations are made inside of the loop`s body
Initializations of control variables must be outside of the loop

11. The Do-While Loop

THE DO-WHILE LOOP
1. Display message "Welcome to C++!” 100 times.
3. Display numbers in reversed order
2. Display counter values
4. Display the odd numbers between 1 and 10

12. loops

LOOPS
Example: Find the sum of the numbers from 1 to 100?
1 + 2 + 3 + 4 + …. + 100 = ?
31
2
6
1
3
0
And so on...

13.

TO BE CONTINUED…