Internal. Every program has a segment. Each segment has a maximum size.
Applications use segment number, and offset. e.g. segment number 3, position 5.
Segmentation fault if program tries to access a bigger memory than segment size. Program destroyed because “illegal”.
Difference between segments and pages
Segments variable size, pages fixed. pages is handled by Operating System or hardware device, segmentation is handled by program. Different fragmentation.
Scheduling