Writing Iteration and Selection Statements

Writing Iteration and Selection Statements

Iteration and selection statements are fundamental building blocks in programming. They allow you to control the flow of your program, execute blocks of code multiple times, and make decisions based on certain conditions.

Iteration Statements

Iteration statements, also known as loops, repeat a block of code a specified number of times or until a certain condition is met. There are two main types of loops:

• For loops: Used when you know the number of iterations in advance.

for (initialization; condition; increment) { // Code to be executed in each iteration }

• Initialization: Sets an initial value for the loop counter.
• Condition: A boolean expression that determines if the loop should continue.

• Increment: Updates the loop counter after each iteration.

• While loops: Used when the number of iterations is unknown and depends on a condition.

while (condition) { // Code to be executed as long as the condition is true }

• Condition: A boolean expression that determines if the loop should continue.

Selection Statements

Selection statements allow your program to choose which code block to execute based on a condition. The most common selection statement is the if-else statement:

if (condition) { // Code to be executed if the condition is true } else { // Code to be executed if the condition is false }

• Condition: A boolean expression that determines which block of code to execute.

You can also use nested if-else statements for more complex decision-making:

if (condition1) { // Code to be executed if condition1 is true } else if (condition2) { // Code to be executed if condition1 is false and condition2 is true } else { // Code to be executed if both condition1 and condition2 are false }

Example

Let's combine iteration and selection statements to create a simple program that finds the largest number in a list:

numbers = [10, 5, 20, 8, 15]

largest = numbers[0]

for number in numbers:
  if number > largest:
    largest = number

print("The largest number is:", largest)

In this example, we:

1. Initialize a variable largest with the first element of the list.
2. Iterate through the list using a for loop.
3. In each iteration, we use an if statement to compare the current number with largest.
4. If the current number is larger than largest, we update largest to the current number.
5. Finally, we print the largest number found.

Key Points to Remember

• Use loops for repetitive tasks.
• Use selection statements to make decisions in your program.
• Plan the flow of your program carefully to ensure that it executes as intended.
• Always test your code thoroughly to catch errors.
• Use meaningful variable names to make your code easier to understand.

By mastering iteration and selection statements, you gain valuable control over the logic and behavior of your programs. These essential concepts are fundamental to creating powerful and efficient applications.