The server operating system manages the resources of the server. It interacts with the network operating system and the data handling software to receive and respond to user requests for services. While there are many choices for the server operating system, currently the most popular are OS/2 and UNIX-based OS. There is also a great deal of interest in Microsoft’s yet-to-be-released Windows Net technology.
These 32-bit operating systems support multithreading and multitasking. A 32-bit processor, such as an Intel 386 or 486, has more address space, a wider physical bus, and larger instruction operand and register sizes than a 16-bit processor like the 80×6 or 80286.
A 32-bit processor’s most important benefit comes from the processor’s larger address space-up to 4G byte, compared with a 16-bit processor’s 16 Mb. limit. But a 32-bit OS is needed to reap this benefit. Software written for DOS or for the segmented architecture of Intel 808x or 80286 chips must manage data and programs in 64-Kb segments. That requires a lot of overhead. A true 32-bit operating system’s large memory address space eliminates that overhead, so programs are faster and more efficient.
OS/2 2.0 and Windows NT provide preemptive multitasking, which means programs that perform time-critical tasks can get control of the processor when they need it. This allows terminal emulation, LAN connectivity, and asynchronous communications programs to run more reliably. For example, when the processor receives an interrupt from a LAN adapter or a modem, the operating system can preempt the program presently running to give the communication software control.
OS/2 2.0 from IBM is supported on most IBM-compatible 386SX micros and above. It has true concurrent multitasking support with data integrity protection. OS/2 2.0 recognizes and uses all available memory, eliminating the DOS-imposed 640 Kb limitation.
Windows 3.x provides cooperative, not preemptive, multitasking. Once the programs get control of the processor, the operating system cannot intervene when another task requires the processor.
Semaphores: (program signals about availability of resources), which prevent one process from writing to a memory location actively used by another process.
Pipes: which allow processes to pass information to each other and it can be temporary or permanent. Pipes operate at the presentation layer of the network architecture and are not hardware or software dependent. Inter-process pipes operate within a single machine. Redirect pipes operate between machines.
A server operating system also provides a runtime support with high performance server applications without the software engineering contingency predicted by some.