There is a fair degree of complexity that cannot be advoided.
Given all the chip types and all the options associated with them MPLAB is not overly complicated.
As a rule I try to be nice, never nasty, and I will try to stick with that. I
suggested you download the OS in another thread and you come here asking what the OS was ?
If you had read the you would not be asking if you need the OS.
My next suggestion is that you do not use the Inchworm without one of the exact chips used in his "Hello World" poster. Doing so will make your first experience much easier.
About bootloader, OS, and debug executive.
What Nigel said is right but let me try to make it a bit clearer.
The bootlaoder is a small program that runs on the Inchworm 16F877. About the only thing it does is allow MPLAB to download sortware (the OS) into the 16F877. A 16F877 will not work in an inchworm without the bootloader.
The OS is loaded by MPLAB to the Inchworm 16F877. The OS is used to communicate with the target chip. The OS used is dependant on the target chip type. You need to download an OS once to start with. Each time you switch between PIC12, PIC16, and PIC18 you need to download a matching OS. Set the MPLAB interface to allow it to do so automatically.
The target chip has a program of its own known as a debug executive. The debug executive is used in conjunction with the onchip debug hardware to step, breakpoint, and run programs on the target. When you program a target MPLAB will download the debug executive for you if needed.
To recap.
- The Inchworm 16F877 must be programmed with a bootloader prior to using it with the Inchworm (ones supplied with kit have this).
- Once you get the Inchworm assembled you have to download the correct OS. See the assembly instruction.