PIC 16F877A Internal Oscillator Enable Problem

[GSFC PIC]

To PIC Masters,
First of all, I am a new PIC [spam], I have been learning a lot from you all PIC experts from this forum, and I am continuing to do so. I realy appreciate your help. So please be patient with me for any nonsense questions. Thanks all in advance

1) I am using PCWH CCS Complier version 3.222 for all files compilation
2) Recently I am using PIC 16F877A and PIC18F452/458 as a learning platform, I realy like these two PICs a lot. My problem is. for PIC16F877A, I am trying to use the Internal Oscillator by using #fuses parameter: INTRC or INTRC_IO, but the CCS complier won't recognize these two parameters, I went on to view the available valid fuses list from the DEVICE Editor, I did not see any INTRC nor INTRC_IO specified, I am trying to add these two parameters in the list but I do not know the MASK and the VALUE # for these two parameters, what should I do, please help ?
3) For PIC18F452/458, how do I use the Internal Oscillator function to run the PIC and what does the command OSCSEN do ? does it switch between the internal and the external oscillator when one or another failed ?
4) What are the advantages and disadvantages for using Internal Oscillator instead of External Oscillator when no CLK out is needed

Please Help

[PCM programmer]

[GSFC PIC]

As usual, you gave good advices. Thanks again !

GSFC PIC