Page physical unit of information, paging is for discrete distribution, reduction in outer fraction memory, improve memory utilization;
Or, simply because the paging system management needs, not the needs of users. Segment is a logical unit of information, which contains a set of relatively complete information about its meaning. The purpose is segmented in order to better meet the needs of users.
The page size is fixed and is determined by the system, the logical address is divided into a page number and the page address two parts, the machine is implemented by hardware, there is only one system and therefore the size of a page. Length of the segment is not fixed, depending on the program written by the user, typically at the source program editing, according to the nature of the information to divide editing program.
Collated address space is one-dimensional, i.e. a single linear space, a programmer need only use mnemonics, can represent an address. Segmented address space is two-dimensional operation, when the programmer identifies an address, requiring both the segment name is given, and the need to give the segment address.