STP Parameter per IS:800-2007

What is the use of STP Parameter in Steel Design as per IS:800-2007?
STAAD.Pro is capable of designing Built-up Sections or Compound Sections, which may be any of the following types –

1. Two or more Rolled Sections welded together
2. A Rolled Section with Plates welded to it
3. Plates welded together to form a section

To identify these types of sections to the design engine for the determination of Section Classification (Refer Figure-2 of the Code), Buckling Class (Table 10, ref. Cl. 7.1.2.2), Imperfection Parameter (Cl. 8.2.2) etc. we need to add some tag with those type of sections. The design parameter STP serves this purpose.
The default value of STP is 1, which means the section is a rolled-section, and the other option is 2, which tags the section as welded / built-up section.
It is always suggested to assign the STP design parameter value 2 to a welded / built-up section.