Problem Statement

Cause a line printer attached to the computer to print a line containing the message:   Hello World!

A line printer is not the same as standard output. A   line printer   was an older-style printer which prints one line at a time to a continuous ream of paper. With some systems, a line printer can be any device attached to an appropriate port (such as a parallel port).

Let's start with the solution:

with Ada.Text_IO; use Ada.Text_IO;

procedure Print_Line is
   Printer : File_Type;
begin
   begin
      Open (Printer, Mode => Out_File, Name => "/dev/lp0");
   exception
      when others =>
         Put_Line ("Unable to open printer.");
         return;
   end;

   Set_Output (Printer);
   Put_Line ("Hello World!");
   Close (Printer);
end Print_Line;