How to learn about uClinux

[zafir]

Hi everyone, I am new to this forum and also first time I am going to use linux operating system. I am student of Industrial Electronics Engineering (3rd Year) and I have no knowledge of linux OS. I am very much interested in embedded systems and main reason of coming to this forum is learn (or seek guidance) about uClinux (Microcontroller Linux). I have programming concept of following languages:
C language (8051, PIC, AVR microcontrollers)
assembly language (8086 processor, 8051 microcontroller)
C++
vhdl (xilinx fpga)

Now I want to learn about uClinux OS and want to run this operating system based application on microblaze softcore 32 bit processor (implemented on spartan3e fpga)
I also want to know that,
why and where we need operating system in embedded systems?
when we can run simple c or assembly program on processor then why we load operating system in processor?
please post any links, pdfs, or any other stuff and also tell me that from where should I start,

Best Regards,
Zafir Hafeez

[RDU]

why and where we need operating system in embedded systems?

It can save you lot of work concentrating on your application and not memory management, drivers, ... It's only usefull on larger processor (ARM, Freescale, Atom, ...). Idealy you need an MMU in the CPU (but not mandatory with uCLinux). If you go to small project on 8 bit processor (8051, AVR, ...) you don't need this.

when we can run simple c or assembly program on processor then why we load operating system in processor?

If you need networking, do you want to write a complete TCP/IP stack and the ethernet chip driver from scratch ? Do you want to run an already stable webserver or write a new one yourself and debug it ? Again, it depend of the project you have.