The most basic division of a computer system is between the hardware and the software. Hardware is often described as the physical part to a computer that you can actually touch with your hands, although that is not recommended especially when the power is on. Software includes all the programed instructions in a computer. There is the main program called the system software, also known as the operating system, which controls and interacts with the hardware and software components. Application software are programs like Photoshop, Internet Explorer, and World of Warcraft. The main hardware components include the CPU or central processing unit, main memory, secondary storage devices, and the input and output devices. The CPU is a microchip that receives and decodes instructions for memory within the CPU are specialized units. One is the arithmetic logic unit. This part performs operations with numbers. The control unit manages the flow of instructions in time with the CPU clock. The faster the CPU clock, the more instructions that can be processed at a time. The processor I have is a quad core. That means that there are four copies of the same transistor circuitry within one chip. With four cores, my processor can execute four times as many instructions at a time than if it only had one core. The main memory is volatile. That means whatever data is held here would be lost if the power went off. Volatile memory needs a constant flow of electricity to work, so it's only used for instructions in active use. Otherwise, data is stored in a permanent storage device like the hard drive. The main memory can be imagined as a sequence of cells that are either empty or contain instructions or data. Each cell has its own unique address. In the actual hardware, electrical signals of on and off represent all computer information. These on and off signals are called bits. The hardware of a computer is like a kitchen. It includes all the equipment necessary for cooking food, as well as an energy source and location for performing the processes of cooking. The kitchen is where the ideas of a recipe are translated into edible meals. A recipe is like software. A recipe is just a series of written instructions that tell you how to turn raw ingredients into a culinary masterpiece. By itself, a recipe is a useless piece of writing. But as soon as the recipe is interpreted and executed, the recipe has a value as a functional tool that can be used again and again to produce the same result. Software is reusable. The instructions of software control the flow of data.