What goes into a computer deciding how many memory locations to assign for specific data types in C?

I have learned file memory management and some very simple CPU assembly for manual memory manipulation, but I feel like there is a gap in my knowledge when it comes to modern, complex computers, OSs, and compilers. What I am wondering is what goes into the decision process to allocate a set amount of memory for different data types. On x86 systems its seems that 8 locations of byte-addressable memory are allocated for pointers consisting of 48-bit addresses. Is the system of allocation similar to that of Linux’s buddy system for files? Why 8 bytes instead of 6? Can it only split in half (limited to powers of 2) or is there a purposeful reason it goes for 8 bytes instead of 6?

I am wondering about the whole process. When you run a program and its program memory is loaded into memory alongside the compile-time set variables, I assume that the compiler has already previously decided based on the computer system how many memory locations to ask for for each variable data type. But how does it decide this?

Any resources you could point me towards would be helpful! Thanks!

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Author: infinity8-room