What exclusive uniqueness do mainframe operating systems have?

The main features of the mainframe operating systems have much uniqueness. The exclusive uniqueness as if security, multitasking, and networking are the main features for the mainframe operating systems. These features make all mainframe operating systems famous in its class. These operating systems are user-friendly. Technically, Windows and Mac OS are for general purpose computing. UNIX is for the pure scientific research purpose. Linux is for the networking purpose. Actually, Linux is a robust server-side operating system. If you compare the operating systems like Windows and Mac OS then Mac OS is strictly for the graphic industry whereas Windows is for pure general purpose computing. However, nowadays, the difference between Windows and Mac OS are squeezing rapidly. Because, the Windows has the maximum number of market shares in the computer world today. Whereas, Mac OS is still far behind it. Nowadays, the computer users follow the Windows footstep. As far as IBM 390 is concerned, it is a 32-bit architecture. The total system memory of this operating system does not exceed 2 GB. Actually, it is called IBM ESA /390, which is introduced in 1990. It supports 32-bit arithmetic instructions. The memory addressing supports up to 31 bit. Therefore, in today's computer world, we love to see and enjoy the enigma of the mainframe computer operating system.