What is a semaphore, and what types are there? Show its uses.

Using a graphics program, develop an entity-relationship diagram for a database application for an Internet bookstore where students buy textbooks from a salesperson and receive invoices for their purchases. Use Figure 5.5 as a guide.

Describe the different types of database requests and transactions.

A new sales ordering system needs a relational database that contains a customer table, a product inventory table, and an order table. Use a word-processing, graphics, or spread-sheet program to draw an entity-relationship diagram showing the relationships among these entities. Next, design each of these tables showing the keys and attributes to be included in each table. Include five sample records for each table.