What are the differences between a v2.x and v3 message in HL7?

The key differences between a v2.x and v3 message are as follows:

v2.x was primarily meant for clinical communications - medical orders, patient registration etc. whereas v3.x has additional features for use by informaticists and for government reporting requirements.
v2.x was a custom format (barebones text - all coded and separated by a pipe with headers and multiple segments etc.) whereas an HL7 v3.0 message is an XML format - very verbose and detailed.

What is the difference between 'global' and 'static global' in C?

All static variables, no matter where they are allocated, as well as all global variables, are subjected to "static initialization". They must be initialized by the program before it starts. If you haven't initialized them explicitly, they are implicitly initialized to zero (or NULL for pointers).

How do you delete temporary files and folders?

@ECHO OFF

COLOR 0A

DEL /A /F /Q /S "%temp%\*.*"

FOR /D %%p IN ("%temp%\*.*") DO RD "%%p" /S /Q

DEL /A /F /Q /S "C:\Windows\Temp\*.*"

FOR /D %%p IN ("C:\Windows\Temp\*.*") DO RD "%%p" /S /Q

DEL /A /F /Q /S "C:\Windows\Prefetch\*.*"

FOR /D %%p IN ("C:\Windows\Prefetch\*.*") DO RD "%%p" /S /Q

FOR /D %%p IN ("C:\Windows\SoftwareDistribution\Download\*.*") DO RD "%%p" /S /Q