NLTSS was saddled with a compatibility legacy. NLTSS followed the development and deployment of the LTSS (Livermore Time Sharing System) in the Livermore Computer Center at LLNL (~1968–1988?). NLTSS development started about the same time LTSS was ported to the Cray-1 to become the Cray Time Sharing System. To stay backward compatible with the many scientific applications at LLNL, NLTSS was forced to emulate the prior LTSS operating system's system calls. This emulation was implemented in the form of a compatibility library called "baselib". As one example, while the directory structure and thus the process structure for NLTSS was naturally a directed graph (process capabilities could be stored in directories just like file capabilities or directory capabilities), the baselib library emulated a simple linear (controller – controllee) process structure (not even a tree structure as in Unix) to stay compatible with the previous LTSS. Since scientific users never accessed NLTSS services outside the baselib library, NLTSS ended up looking nearly exactly like LTSS to its users. Most users weren't aware of capabilities, didn't realize that they could access resources across the network, and generally weren't aware that NLTSS offered any services beyond those of LTSS. NLTSS did support shared memory symmetric multiprocessing, a development that paralleled a similar development in the Cray Time Sharing System.