Chapter 2: Computer Architecture

Before learning how to program, you need to first understand how a computer interprets programs. You don't need a degree in electrical engineering, but you need to understand some basics.

Modern computer architecture is based off of an architecture called the Von Neumann architecture, named after its creator. The Von Neumann architecture divides the computer up into two main parts - the CPU (for Central Processing Unit) and the memory. This architecture is used in all modern computers, including personal computers, supercomputers, mainframes, and even cell phones.

Structure of Computer Memory

To understand how the computer views memory, imagine your local post office. They usually have a room filled with PO Boxes. These boxes are similar to computer memory in that each are numbered sequences of fixed-size storage locations. For example, if you have 256 megabytes of computer memory, that means that your computer contains roughly 256 million fixed-size storage locations. Or, to use our analogy, 256 million PO Boxes. Each location has a number, and each location has the same, fixed-length size. The difference between a PO Box and computer memory is that you can store all different kinds of things in a PO Box, but you can only store a single number in a computer memory storage location.

Memory locations are like PO Boxes

You may wonder why a computer is organized this way. It is because it is simple to implement. If the computer were composed of a lot of differently-sized locations, or if you could store different kinds of data in them, it would be difficult and expensive to implement.

The computer's memory is used for a number of different things. All of the results of any calculations are stored in memory. In fact, everything that is "stored" is stored in memory. Think of your computer at home, and imagine what all is stored in your computer's memory.

• The location of your cursor on the screen

• The size of each window on the screen

• The shape of each letter of each font being used

• The layout of all of the controls on each window

• The graphics for all of the toolbar icons

• The text for each error message and dialog box

• The list goes on and on...

In addition to all of this, the Von Neumann architecture specifies that not only computer data should live in memory, but the programs that control the computer's operation should live there, too. In fact, in a computer, there is no difference between a program and a program's data except how it is used by the computer. They are both stored and accessed the same way.