Local users, modem users, and network users can all simultaneously run text and graphics programs. Memory Required Linux has security systems to prevent normal users from misconfiguring the system. Although Windows NT isn't multiuser, it has security checks for the individual using the machine. Linux's security and multiuser features are so well developed because they are traditional features for Unix. Every feature supported will tend to make an operating system larger, consuming more memory and storage.
Larger systems are also slower than smaller systems when memory is scarce.
So the size of a system is an important issue. NT is the largest of the three systems. NT's support for portability, multiprocessing, and many other features is the cause of its large size. Given a powerful enough machine, NT offers a set of features that is very compelling. For most the graphical interface will be worth the cost in resources.