Input and Output in Pseudocode

Input and output operations are fundamental in programming. In pseudocode, we use specific keywords to represent these operations, allowing us to describe how a program interacts with users or external data sources.

Input

Input operations are used to get data from the user or an external source. The common syntax for input in pseudocode is:

INPUT variable

Example:

INPUT name
INPUT age

This pseudocode asks the user to input their name and age, storing the values in the variables 'name' and 'age' respectively. For more information on how to handle variables, refer to the Variables in Pseudocode guide.

Output

Output operations are used to display data to the user or send it to an external destination. The common syntax for output in pseudocode is:

OUTPUT expression

Example:

OUTPUT "Hello", name
OUTPUT "You are", age, "years old."

This pseudocode displays a greeting using the 'name' variable and states the user's age using the 'age' variable.

Combined Example

Here's an example that combines both input and output operations:

INPUT name
INPUT age
OUTPUT "Hello", name
OUTPUT "You are", age, "years old."
IF age >= 18 THEN
    OUTPUT "You are an adult."
ELSE
    OUTPUT "You are a minor."
END IF

This pseudocode asks for the user's name and age, greets them, states their age, and then determines if they are an adult or a minor based on their age. For more details on decision-making structures, check the If Statements in Pseudocode guide.

Input Validation

It's often necessary to validate user input. Here's an example of how you might do this in pseudocode using a while loop:

INPUT age
WHILE age < 0 OR age > 120
    OUTPUT "Invalid age. Please enter a value between 0 and 120."
    INPUT age
END WHILE

OUTPUT "Valid age entered:", age

This pseudocode ensures that the user enters a valid age between 0 and 120. It will keep prompting the user until a valid age is entered. For more information on loops, refer to the Loops in Pseudocode guide.

Another Example: Validating a Menu Choice

OUTPUT "Menu:"
OUTPUT "1. Option A"
OUTPUT "2. Option B"
OUTPUT "3. Option C"

INPUT choice
WHILE choice < 1 OR choice > 3
    OUTPUT "Invalid choice. Please enter 1, 2, or 3."
    INPUT choice
END WHILE

OUTPUT "You selected option", choice

This example validates a menu choice, ensuring the user enters a number between 1 and 3.

Best Practices

Always provide clear prompts for input operations
Validate user input when necessary
Use meaningful variable names for input data
Format output for readability
Use loops for input validation to ensure correct data entry