Hello world and simple gnatmake

Hello World

• hello.adb (and prettified)

     --  Our first Ada program!
     with Ada.Text_IO;
     procedure hello is
     begin
        Ada.Text_IO.put_line("Hello students in ITEC 320!");
        Ada.Text_IO.put_line("I hope you have a great semester!");
     end hello;
  
     // Java equivalent:
     public class Hello{
        public static void main(String args[]){
           System.out.println("Hello");
           System.out.println("Have a great semester!");
        }
     }
  

Notes on hello.adb

• -- starts a comment to end of line
• Ada.Text_IO is a I/O library
• semicolons similar to Java
• Name: hello
• A procedure is similar to a Java method
• procedure hello is comparable to psv main in Java
• You choose the main procedure's name (any identifier)
• File name (hello.adb) matches the procedure name (hello)
• Execution starts at hello's begin statement
• Different from Java:
• No multi-line comments
• With is required to access library
• No class
• You choose name of main procedure
• begin/end instead of braces (ie {})

Compile and Run from Command Line

• Assume gnat system is installed


• Compile: gnatmake hello
• run: hello


• Alternate ways to compile and run:
• Compile: gnatmake hello.adb
• Run: ./hello
• "./" is required on many linux and mac systems

More on Compile and Run

• Creates executable:
• hello on linux/mac
• hello.exe on windows


• Also creates hello.o and hello.ali:


• Runs directly on hardware
• nothing equivalent to java Hello