A computer system in which two or more CPUs works concurrently and access a common RAM is called multiprocessor OS.

Multiprocessor Operating System uses two or more central processing units (CPU) within a single computer system. These multiple CPUs have strong communication by sharing the computer bus, memory, and other peripheral devices. These systems are referred to as tightly coupled systems.

These types of systems are used when very high-speed applications are required to process a large volume of data. These systems are generally used in an environment like satellite control, weather forecasting, etc. The basic structure of the multiprocessing system is shown in the figure below.

Key design challenges:

• The correctness of (shared) data structures
• Scalability
• Partitioning
• Scheduling