Input and Output

NeoObjectPascal offers simple procedures for interacting with the console: WriteLn to display information, ReadLn to read data from the user, and showMenu to build numbered menus.

Writing with WriteLn

The WriteLn procedure writes a line of text to the console and adds a line break at the end:

begin
    WriteLn("Olá, Mundo!");
end.

Saída

 Olá, Mundo! 

Multiple arguments

WriteLn accepts several arguments and concatenates them with no separator in the output. This is useful for building messages with dynamic values:

var nome: String;
var idade: Integer;

begin
    nome := "Carol";
    idade := 28;
    WriteLn("Olá, ", nome, "! Você tem ", idade, " anos.");
end.

Saída

 Olá, Carol! Você tem 28 anos. 

Blank line

Calling WriteLn() with no arguments prints just a line break — handy for separating blocks of output.

Reading with ReadLn

The ReadLn procedure reads a line typed by the user and stores it in a variable. The value is converted to the type of the target variable:

var nome: String;

begin
    WriteLn("Qual é o seu nome?");
    ReadLn(nome);
    WriteLn("Prazer, ", nome, "!");
end.

Saída

 Qual é o seu nome? Prazer, Ada! 

When the target variable is Integer or Real, the text read is automatically converted to the corresponding numeric type:

var idade: Integer;

begin
    WriteLn("Digite sua idade:");
    ReadLn(idade);

    if idade >= 18 then
        WriteLn("Maior de idade.")
    else
        WriteLn("Menor de idade.");
end.

Saída

 Digite sua idade: Maior de idade. 

Type conversion

When reading into a numeric variable, make sure the input is actually a number. Unexpected input can cause conversion errors — handle these cases with try/catch when reading untrusted data. See Error Handling.

Menus with showMenu

The showMenu procedure takes a list of options and prints a numbered menu automatically:

begin
    showMenu("Café", "Chá", "Suco");
end.

Saída

 1. Café 2. Chá 3. Suco 

Combine showMenu with ReadLn to build a selection interface:

var opcao: Integer;

begin
    showMenu("Novo pedido", "Consultar", "Sair");
    WriteLn("Escolha uma opção:");
    ReadLn(opcao);

    if opcao = 1 then
        WriteLn("Iniciando novo pedido...")
    else if opcao = 2 then
        WriteLn("Consultando...")
    else
        WriteLn("Até logo!");
end.

Saída

 1. Novo pedido 2. Consultar 3. Sair Escolha uma opção: Iniciando novo pedido... 

Best practices

• Use WriteLn with multiple arguments instead of concatenating everything with +: it is more readable and avoids manual conversions.
• Always display a message before a ReadLn so the user knows what to type.
• When reading numbers, consider validating or handling conversion errors.

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