The two pointers per number of a doubly linked list prepare programming quite easy. Singly linked lists as like the lean sisters of doubly linked lists. We need SItem to consider to an item in a singly linked list. SItems delete the predecessor pointer and only locate a pointer to the successor node. This creates singly linked lists more space ef_cient and usually faster than their doubly linked brothers. The downside is that some operations may no longer be performed in constant time or may no longer be supported in full way. We can replace an SItem only if we know its predecessor. We collect the implementation approach from doubly linked lists. SItems form collections of cycles and a SList has a dummy SItem h that precedes the _rst proper component and is the successor of the last proper component. Many operations of Lists can still be operated if we slightly modify the interface.