Fix my C program - using RPI for GPIO programming on Raspberry Pi 4

I have a C program that uses RPI i/f to program GPIOs on Raspberry Pi. Downloaded it from the net. But it's for older models that use BCM2835.
Raspberry Pi 4 uses BCM2711. This is causing me difficulty in understanding and porting the program.

I am attaching the program files (which could be erroneous), BCM2835 datasheet, and the BCM2711 datasheet.