The processor in a personal computer is also known as the Central Processing Unit (CPU), and you can think of it as the PC's "brain". The processor does exactly what the name implies it does: it processes instructions. It processes instructions and manipulates data after fetching them from the PC's RAM (random access memory), and the PC could not function without it. At this point I believe I have answered the question adequately, however I think it would be appropriate to discuss some aspects of the processor that are important to understand; all of them relate to performance. Brand - The two major processor manufacturers these days are Intel and AMD, and there are a few key differences between an Intel processor and an AMD processor. The biggest difference (in my opinion, at least) between them is their design; basically, AMD processors "get more done" per clock cycle (I will talk about clock cycles next) than Intel processors. People tend to look at a processor's raw internal clock speed more than anything else, and an AMD processor's description mentions not only its actual internal clock speed, but a "rating" number that equals how fast the AMD processor is compared to an Intel processor. For example, an AMD Athlon XP 1900+ has an internal clock speed of 1.60 gigahertz, but its performance is equal to that of an Intel processor running at 1.90 gigahertz. AMD processors are cheaper than Intel processors, but AMD processors have also had a history of heat problems (although this is less of a problem now than it was before). AMD processors have the advantage of being more "efficient", but Intel processors have the advantage of higher raw internal clock speeds and higher front side bus speeds (discussed later). The question of which brand of processor is "better" has many answers, but the average PC user shouldn't notice a big performance difference between an Intel processor and an AMD processor that has a rating equal to the Intel's internal clock speed. It really depends on what processors are out there and what the user wants to do on their system. Internal and external clock speeds - The internal clock speed is the aspect of the processor in a personal computer that gets the most attention from the average PC user. The internal clock speed is a measure of how many times the processor "thinks" per second, in hertz (measure of frequency). If your computer's processor has an internal clock speed of 2000 megahertz (2.0 gigahertz), that means that the processor operates at 2 billion cycles per second. Faster processors usually offer greater performance, but that isn't always the case since there are other factors to consider, like the processor's internal design and the applications being run on the system. The processor's internal clock speed is calculated by multiplying a multiplier times the speed of the system clock. The processor communicates with the other components in the computer at lower speeds (all derived from the system clock), and the speed that most people are probably familiar with is the speed of the system clock itself. The speed of the system clock itself is a measure of the speed of the "front side bus", the path that data travels on between the processor and memory. The processor's internal clock speed is important, but often the speed of the system clock is more important; performance will suffer if the processor has to communicate with other devices in the system at slower speeds. In other words, increasing the speed of the system clock instead of increasing the processor's internal speed can often mean better performance. Level 1 and Level 2 cache - The purpose of these two "caches" (small but fast memory chips) is to allow the processor to access data and instructions quickly without having to go to the system memory to get them. If the processor needs something and it can't be found in the L1 cache (accessed first) or the L2 cache (accessed second), it has to be retrieved from the system memory, which is slower than retrieving it from a cache. When shopping for a processor, keep in mind the speed and size of the caches. Width of the registers - A register, in terms of computer processors, is a place that data being manipulated is put into. The "width" of the register is measured in bits (computers work in the binary number system, and a binary bit has a value of 1 or 0), and processors today either have a register width of 32 bits or 64 bits, with the former width being much more common. When somebody says that a processor is 32 bits, they're saying that the register width is 32 bits, and that's how much data the processor can work with at one time. 64-bit processors can work with 64 bits of data at a time, and whether or not a 64-bit processor yields better performance than a 32-bit processor depends on what software you're using; the software (including the operating system) needs to be designed to take advantage of a 64-bit processor. For now, most people should be able to get things done and have fun on computers with 32-bit processors. Width of the data bus - The width of the processor's data bus (width in bits) is important because it determines how much data can be put out per second (bandwidth), along with the speed (in megahertz these days) of the bus. Modern 32-bit processors have a data bus width of 64 bits, and some people get confused by this; they say that the processor is 64 bits, when that refers to the data bus width, NOT the width of the processor's internal registers. EDIT: In my description of the processor's internal clock speed, I mistakenly said that 2000 hertz equals 2.0 gigahertz. 2.0 gigahertz is equal to 2000 MEGAhertz. I apologize for the error and any confusion that may have stemmed from it.

CPU is responsible for handling instructions and calculation it receives from other hardware components in the computer and software programs running on the computer

A processor is the logic circuitry that responds to and processes the basic instructions that drive a computer. The term processor has generally replaced the term central processing unit (CPU). The processor in a personal computer or embedded in small devices is often called a microprocessor.

Not a clue

All processors process messages. Messages orginate from sensors. The output of all processors are signals to operated actuators. So the process is this. *******The Processor general process******** Sensor ------ Selective message from the world. Processor --- Decide what to to do with that message. Actuator ---- Modify the world. **************************** Thus all processors are message processors. A processor is where the abstract (message) interacts with the real (world) / (universe). A very important place!!! "Modify the world" could be write a file to disc, place a weld at x,y,z, or go to work.