Simple Module Development

helloworld.info

name = Hello World!
description = A simple module example
core = 7.x
version = "7.x-1.0"

helloworld.module

<?php

function helloworld_menu(){
	$items = array();
	$items['hello/world'] = array(
		'page callback' => 'hello_world_page'
	);
	$items['admin/helloworld'] = array(
		'title' => 'Hello World Admin',
		'page callback' => 'drupal_get_form',
		'page arguments' => array('helloworld_admin'),
		'access arguments' => array('access administration pages')
	);
	return $items;
}

function helloworld_admin(){
	$form = array();
	$form['helloworld_message'] = array(
		'#type' => 'textfield',
		'#title' => "Hello World Message",
		'#description' => "Message to be displayed",
		'#required' => TRUE,
		'#default_value' => variable_get('helloworld_message', "Hello World!");
	);
	return system_settings_form($form);
}

function hello_world_page(){
	return variable_get('helloworld_message', "Hello World!");
}