Hardware reference guide

Chapter 3: The Software
The Shell
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7535 Hardware Reference Guide
• Suspend Threshold
This is the percentage of battery charge left when the unit executes the Run-
to-Suspend transition. This setting is on the Suspend Threshold tab of the
Power Properties dialog. Possible settings are: 0 to 50 percent, in 5% steps.
3.3 The Shell
3.3.1 Overview
The shell is responsible for providing an interface to the user for access to the termi-
nal’s applications, files, and configuration. It also monitors and provides notifica-
tions to the user about the system state.
3.3.2 System Structure
The shell is the first user application run by the system. It registers several windows
with the operating system and has several responsibilities defined by the OS. These
responsibilities include monitoring system memory and power levels. Along with
the tasks that are required by the OS, the shell is responsible for providing the user
with usability features. These features include a notification area, a window that dis-
plays currently running tasks and a method to run applications.
The shell is a multithreaded application. Information is passed between the threads
using Windows CE graphical window and event system (GWES) and shell-defined
message types. Certain parts of the shell must register with the OS to receive special
messages.
3.3.2.1 The System Monitor
The system monitor task contains one window to receive messages and can poten-
tially be multithreaded. Each thread can be used to monitor a system resource. The
initial design has only one thread that monitors system memory and power. This
thread is woken up periodically and checks the system resources.