#pragma statements in PIC18F4550 C programming
Microchip PICs requires certain configuration settings to be defined before the microcontroller powers up. For example, the oscillator selection  and whether code protection is enabled. These configuration settings are stored in a special place in memory and can only be altered during a programming sequence. Not during normal operation of the PIC.

Since these configuration settings are dealt with in a special way in memory, each compiler has it's own way of handling them. It is not standard C, so there is no universal syntax. It differs from compiler to compiler, but every compiler designed for PIC microcontrollers will provide some way to program the configuration settings. The only way to get the definitive syntax is to read the compiler's user's manual.

You can find all if the configuration settings for the specific PIC you're working on in the "Special Features" section of the datasheet. Every family of PICs have different settings, so the #pragma (or whatever your compiler uses) values are not usually portable from one PIC to another, even with the same compiler.

So in summary, you must first learn the proper syntax for your specific compiler to define configuration settings. And then you must read the Special Features section of the datasheet of the specific PIC you're using to find out which configuration settings are applicable.