Teachers can use tools like PowerPoint to present concepts visually and allow students to use computers and word processors to enhance their learning. Blackboards were originally made of slate but are now often green. Laptop computers are portable personal computers that can be closed for transportation and provide portability and battery power. Books are a primary source of historical or current information and can have a long life. Visual aids should be used by educators as tools to effectively convey ideas but not relied on completely for teaching.