Processes enable users to open and work in several applications at the same time. For example, a user can edit a file in a text editor while another application is recalculating a spreadsheet.

As a preemptive multitasking OS, Windows Mobile supports multiple processes running simultaneously on the system.

There is no limit to the number of processes that can run on a Windows phone. The only limit is the amount of available system resources.

A thread is the basic unit to which the OS allocates processor time. Threads have the following characteristics:

• They enable an application to perform more than one task at a time, even though applications cannot run more than one thread at a time.
  
  
• They can run any part of the process code, including parts that are being run by another thread.
  
  
• Although one thread is designated as the primary thread for the process, a process can also create an unspecified number of additional threads.
  
  
• Available system resources limit the number of threads.
  
  
• Windows Mobile provides 256 priority levels that you can set for a thread. To assign priority levels, Windows Mobile uses the following functions:
  
  
  • CeSetThreadPrioritysets the priority for a specified thread.
    
    
  • CeGetThreadPriorityreturns 0 (zero) as the highest priority and 255 as the lowest priority.
    
    
• If an OEM enforces a trusted environment, Windows Mobile can protect the top 248 priority levels from applications.
  
  

Because Windows Mobile supports preemptive multitasking, it creates the effect of a process simultaneously running multiple threads. When a process has more than one thread running, the OS rapidly switches from one thread to another so that the threads appear to run simultaneously.