Paging: Pages are physical units, which are mainly established for the system's memory management needs and do not consider the logical structure of the program.
Segmentation: Segments are logical units, and each segment contains a relatively complete set of logically meaningful information. Segmentation management is designed to better meet the needs of programmers and the structure of the program.
Fixed size
Paging: The size of a page is fixed, determined by the operating system or hardware, so all pages have the same size in the entire system.
Segmentation: The size of a segment is unfixed, defined by the programmer or determined by the compiler based on the logical structure of the program, and the sizes of different segments can be different.
Structure of address space
Paging: The job address space in a paging system is one-dimensional, and the logical address of each page is continuous, that is, the address within the page is continuous.
Segmentation: The job address space in a segmentation system is two-dimensional, and the addresses between segments are discontinuous, because each segment is divided according to logic, and there is no continuity between segments.