I need information about embdded computing system

Embedded system designer design both hardware and software

Q.1what is embedded computing system
Q.2 what is specification for embedded system
Q.3 what is requirement for embedded system

I did this

1.embedded computing system- it is combination of hardware and software that is use to perform dedicated task

2.specification
which processor does system need
how much rom is used to store program
how much ram should be used

3.requirement
system should be low cost
system should be low power consumption
system should be fast
system should be reliable

I need more information can anyone give link where I can learn in detail

There are lots of ebooks on embedded system. But, i suggest before that learn 8085 microprocessor from author Ramesh Gaonkar and then 8051 microcontroller from author Ayala. They are fairly simple to understand. Once you build enough knowledge, on microcontrollers, go through embedded system ebooks, no specific author. And start making simple applications like toys, mixers etc.
For eg. If wants to design a simple household mixer or grinder. First define output, that a pot with rotating blade powered from 230V AC, with variable speed. SO, for rotation you need a motor, in our case a simple BLDC motor will suffice, power can be rectified into DC from 230V and then for variable speed a speed controller for BLDC motor is required.
This example is available in microchip.com website but i don't know the application note number.