Designing a Pascal Program to Validate User Input and Provide Feedback

Designing a Pascal program to validate user input and provide meaningful feedback can be both educational and fun. This guide will walk you through creating a Pascal program that checks if a number entered by the user is between 1 and 5, and outputs the corresponding name or a message indicating an invalid input.

Introduction

Developing a Pascal program to handle user input and provide output based on specific criteria is a common task in programming education. This article will cover the fundamental steps and provide a practical example to help you understand and implement such a program.

Step-by-Step Guide to Create the Program

1. Program Declaration

Start by declaring your program:

program CheckNumber;

2. Variable Declaration

Declare an integer variable to store the user's input:

var
  number: Integer
end.

3. Input Prompt and Reading User Input

Prompt the user to enter a number between 1 and 5:

Write('Enter a number between 1 and 5: ');
ReadLn(number);

Read the input from the user:

ReadLn(number);

4. Case Statement for Input Validation

Use a case statement to check the value of the input and provide the corresponding output:

case number of
  1: WriteLn('You entered: One');
  2: WriteLn('You entered: Two');
  3: WriteLn('You entered: Three');
  4: WriteLn('You entered: Four');
  5: WriteLn('You entered: Five');
  else
    WriteLn('Invalid input. Please enter a number between 1 and 5.');
end;

5. End of Program

Close the program:

end.

Example Code

program CheckNumber;
var
  number: Integer;
beginc
  Write('Enter a number between 1 and 5: ');
  ReadLn(number);
  case number of
    1: WriteLn('You entered: One');
    2: WriteLn('You entered: Two');
    3: WriteLn('You entered: Three');
    4: WriteLn('You entered: Four');
    5: WriteLn('You entered: Five');
  else
    WriteLn('Invalid input. Please enter a number between 1 and 5.');
  end;
end.

Making it Fun with Custom Functions

Now, let's make it a little more challenging and fun by using custom functions and lists. Here's a modified program that uses a list of words and a custom function to output them based on user input:

1. Program and Unit Declarations

program Fun;
uses
  Classes;
function SayTheWord(aWord: String): String;
var
  i: String;
begin
  for i in aWord do
    write Chr(ord(i) - 1);
  writeln;
end;
var
  number: integer;
  words: String;
  list: TStringList;
begin
  words : 'pofuxpuisffgpvsgjwf';
  list : ;
  list.Text : words;
  repeat
    write('Enter a number [1-5] 0 to stop: ');
    readln(number);
    if number  1 then
      SayTheWord(list[0]);
    if number  2 then
      SayTheWord(list[1]);
    if number  3 then
      SayTheWord(list[2]);
    if number  4 then
      SayTheWord(list[3]);
    if number  5 then
      SayTheWord(list[4]);
  until number  0;
  writeln('Goodbye!');
end.

2. Explanation of the Code

This program declares a custom function SayTheWord that takes a string as input and outputs a modified version of the string. It also uses a TStringList to store a list of words.

The program prompts the user to enter a number between 0 and 5. Depending on the input, it calls the SayTheWord function with the corresponding word from the list. If the user enters 0, the program exits with a goodbye message.

Conclusion

Designing and implementing a Pascal program that validates user input and provides feedback can be both educational and engaging. By following the steps in this guide, you can create a robust and user-friendly program. Experiment with different inputs and functions to enhance your programming skills and make your programs more interesting for users.

Keywords

Pascal programming, user input validation, output customization