Essay code samples

1.essay.asm

                ; com files are always loaded at 100h address
                ORG 100h

start:          ; make sure data segments and extra segments point
                ; to the same segment as the code, since this is a
                ; com app
                MOV AX,CS
                MOV DS,AX
                MOV ES,AX

                JMP readkey

invalidkey:     ; print error message
                MOV AH,9
                MOV DX, errormessage
                INT 21h

readkey:        ; print inputmessage
                MOV AH,9
                MOV DX, inputmessage
                INT 21h

                ; read key from keyboard, result is stored in AL
                MOV AH,1
                INT 21h

                ; if it is smaller then 'a' go to invalidkey label
                CMP AL,'a'
                JL  invalidkey

                ; if it is larger then 'z' go to invalidkey label
                CMP AL,'z'
                JG  invalidkey

                ; set lowerval in the output sting
                MOV [lowerval],AL

                ; make AL uppercase
                ADD AL,'A'-'a'

                ; set upperval in the output sting
                MOV [upperval],AL

                ; print outputmessage
                MOV AH,9
                MOV DX, outputmessage
                INT 21h

                ; Terminate app
                INT 20h

inputmessage    db 0Dh,0Ah,"Please enter a lowercase letter (a-z): $"

errormessage    db 0Dh,0Ah,"Invalid input: this is not a lowercase letter!$"

outputmessage   db 0Dh,0ah,"The uppercase of "
lowerval        db 0
                db " is "
upperval        db 0,0Dh,0Ah,"$"  

2.essay.pas

Program Essay;
uses SysUtils,Crt;

function ReadLowercaseLetter():char;
begin
  while true do
    begin
      writeln('Please enter a lowercase letter (a-z):');
      ReadLowercaseLetter := ReadKey;
      if (ReadLowercaseLetter in ['a'..'z']) then
        exit
      else
        writeln('Invalid input: this is not a lowercase letter!');
    end;
end;

var
   letter:char;
begin
   letter := ReadLowercaseLetter();
   writeln('The uppercase of '+letter+' is '+UpperCase(letter));
end.

3.essay.cs

using System;

namespace Essay
{
    public class EssayConsole
    {
        char letter;

        public void ReadLowercaseLetter()
        {
            while (true)
            {
                Console.WriteLine("Please enter a lowercase letter (a-z):");
                var key = Console.ReadKey().KeyChar;
                if (key >= 'a' && key <= 'z')
                    return;
                else
                    Console.WriteLine("Invalid input: this is not a lowercase letter!");
            }
        }

        public void WriteLastReadLetterAsUppercase()
        {
            Console.WriteLine("The uppercase of {0} is {1}",letter,letter+'A'-'a');
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            var console = new EssayConsole();
            console.ReadLowercaseLetter();
            console.WriteLastReadLetterAsUppercase();
        }
    }
}

essay.f#

#light
open System

let ucase x = x.ToString().ToUpper()
let islowercase x = x >= 'a' && x <= 'z'

let rec getlcasechar _ = 
    printfn "Please enter a lowercase letter (a-z):"
    let letter = (Console.ReadKey().KeyChar);
    printfn""
    if islowercase(letter) then 
        letter
    else
        printfn("Invalid input: this is not a lowercase letter!")
        getlcasechar() 
        
let lcasechar = getlcasechar()

printf "The uppercase of %c is %s" lcasechar  (ucase lcasechar)

essay.fs

#light
open System

let ucase x = x.ToString().ToUpper()
let islowercase x = x >= 'a' && x <= 'z'

let rec getlcasechar _ = 
    printfn "Please enter a lowercase letter (a-z):"
    let letter = (Console.ReadKey().KeyChar);
    printfn""
    if islowercase(letter) then 
        letter
    else
        printfn("Invalid input: this is not a lowercase letter!")
        getlcasechar() 
        
let lcasechar = getlcasechar()

printf "The uppercase of %c is %s" lcasechar  (ucase lcasechar)