Flash Storage; Ffs Partitions; Working With Ffs Partitions - Symbol MC50 User Manual

6-18 MC50 Integrator Guide

Flash Storage

In addition to the RAM-based storage standard on Windows CE mobile computers, the mobile computer also contains a non-volatile
Flash-based storage area which can store data (partitions) that a cold boot cannot corrupt. This Flash area is divided into two
categories: Flash File System (FFS) Partitions and Non-FFS Partitions.

FFS Partitions

The mobile computer includes two FFS partitions which appear to the mobile computer as a hard drive that the OS file system can
write files to and read files from. Data is retained even if power is removed.
The two FFS partitions appear as two separate folders in the Windows CE file system and are as follows:
• Platform: The Platform FFS partition contains Symbol-supplied programs and Dynamic Link Libraries (DLLs). This FFS is
configured to include DLLs that control system operation. Since these drivers are required for basic mobile computer
operation, only experienced users should modify the content of this partition.
• Application: The Application FFS partition stores application programs needed to operate the mobile computer.

Working with FFS Partitions

Because the FFS partitions appear as folders under the Windows CE file system, they can be written to and read like any other folder.
For example, an application program can write data to a file located in the Application folder just as it would to the Windows folder.
However, the file in the Application folder is in non-volatile storage and is not lost on a cold boot (e.g., when power is removed for a
long period of time).
Use standard tools such as ActiveSync to copy files to and from the FFS partitions. They appear as the "Application" and "Platform"
folders to the ActiveSync explorer. This is useful when installing applications on the mobile computer. Applications stored in the
Application folder are retained even after cold-booting the mobile computer, just as the MC50 Demo program is retained in memory.
The Windows CE image includes two device drivers to assist developers in configuring the mobile computer following a cold boot:
RegMerge and CopyFiles.
RegMerge.dll
RegMerge.dll is a built-in driver that allows registry edits to be made to the Windows CE Registry. Regmerge.dll runs very early in the
boot process and looks for registry files (.reg files) in certain Flash File System folders during a cold boot. It then merges the registry
changes into the system registry located in RAM.
Since the registry is re-created on every cold boot from the default ROM image, the RegMerge driver is necessary to make registry
modifications persistent over cold boots.
RegMerge is configured to look in the root of two specific folders for .reg files in the following order:
\Platform
\Application
Regmerge continues to look for .reg files in these folders until all folders are checked. This allows folders later in the list to override
folders earlier in the list. This way, it is possible to override Registry changes made by the Platforms partitions folders. Take care when
using Regmerge to make Registry changes. The DCP for MC50 contains examples of .reg files.
Regmerge only merges the .reg files on cold boots. A warm boot skips the merge process.