I would like to write some program or Embedded-C on 8051 MC. Programs like ISR, LED blinking, Round Robin, and all. Is it possible without hardware? Only keil uvision4 hardware simulator is sufficient to write the program? Please help.
The Keil simulator simulates the core and the peripherals and can be used for instruction cycle level timing. It does not simulate the external hardware that you might attach to the device itself. In theory you can attach debug scripts to simulate external devices, but sit is a lot of work.
As far as a blinking LED is concerned the best you will do with the Keil simulator is observe a bit in a GPIO register changing from 0 to 1.
Simulating interrupts is (I believe) simply a case of setting the interrupt flag in the appropriate peripheral.
In short you can probably do it, but it is not much fun and may put you off embedded development altogether.
A Silicon Labs ToolStick starter kit is US$24.99, and comes with the Keil tools and SiLabs' IDE, so that would be a more interesting way to start perhaps. The hardware includes an LED, a switch, a potentiometer, and solder pad access for all I/O pins to extension. If you are a potential business prospect SiLabs often give these out for free.