DSP Vs MicroP Vs Microcontroller? ANy rule of thumb?

Hi

I have some basic idea about these processors and controllers. I find a lot of info on the internet and now I have an idea as to how they differ. DSPs and Microprocessors in their architecture and functionality and controllers with their ability to hold program memory, thereby execute more specific operations like in Pulse Width Modulation etc.,

But I still do not have a practical Idea as to which of these I need to think of for each type of needs.. I mean is there any rule of thumb wherein I can figure out which of these could be handy depending on what I'm building? Like controllers for stepper motors, Some digital stuff DSPs and computers have processors.. What the input is, what the output is and how each of these help when I'm building something..?

Basically microcontroller and DSP have a similar sequential architecture. While the microcontroller is more tailored toward byte and bit handling, the DSP is optimized for very fast signal processing tasks (DSP = digital signal processing). This was caused in the beginning by the fact, that semiconductor technology was limited. These days it is in most cases not true anymore and an lot gets mixed up. So microcontroller get some DSP functionality (like hardware multiplier) and DSPs get more word, byte and bit handling capability. In some cases a microcontroller does all the data handling and on the same chip you have a DSP integrated for signal processing function(mostly the case in smart phones). As a consequence of this technology advances microcontroller can be used also in lower end digital signal processing tasks and the way around. So a microcontroller tailored for (stepper) motor control can do most task. If you have however very complex control algorithm a DSP tailored for motor control has a higher performance.

Enjoy your design work!

DSP are more complicated processors capable of handling more complex problems. They usually have pipelining implemented and they carry MAC (Multiply-Accumulator) units. They have more than one ALU's and are capable of handling Floating as well as Fixed number calculations.
uP are subset of DSP processors but with limited functionalities. Also used in Embedded Products
uC are used in Embedded products and Consumer Electronics. THey are cheap but they have high advantage of implementing complex things with a huge circuitry attached/interfaced.

Thanks a lot!

From the replies, I'm getting a sense of where and why they're used. My understanding is that DSP is all about getting in some digital data and then performing some complex calculations as needed and get it to the output..More of repeated calculations in some sense..like music, digital stuff.. Then microcontrollers too use DSPs if at all for the complex calculations. And mircroprocessors are for embedded electronics for some preprogrammed output although microcontrollers dominate the consumer electronics segment I suppose. And when an extra functionality or brain is needed, a uP comes into picture..
Thats how I roughly see it and i'll look into the details of these as I begin some practical work..THe above replies have given some direction>! thanks