Side-by-side execution

Side by Side Excution enables the existence of multiple
versions of .Net Framework on the same machine at the same
time and also multiple versions of applications that use a
version of the .Net Framework.

Also the side by side implenetation requires the use of a
startup Shim.
Shim is a thin piece of code that accepts a Version No and
other start up parameters from host to start the CLR.

Startup shim is implemented in the mscoree.dll.
Only one version of the shim exists in the machine and is
available in the System 32 folder.