What Is in Partition IIB (Chapter 5)

The four sections (21 through 24) of Partition II that constitute Chapter 5 in this book present all the details of the file format that are needed for building purely managed, portable applications. Also included are features that permit writing managed code that is not portable, such as code that calls through to the underlying operating system.

The sections in the standard were written in the order of smallest data structure to largest data structure:

• Section 21 defines the metadata tables. Metadata is stored in a file derived from relational databases, and these tables contain most of the information that we refer to as metadata.

• Section 22 defines the values of various bitmasks and flags that are used in the metadata tables described in section 21. It also defines the formats of information referenced from these tables but not stored directly in the tables themselves (stored as "blobs," in database terminology). It further amplifies the description of metadata tables in section 21 with descriptions of other structures used in those tables:

  • Signatures

  • Custom attributes

  • Marshalling descriptors

• Section 23 describes the metadata layout inside the PE file.

• Section 24 describes the CLI extensions to the PE file format and enough description of a subset of the PE format that a tool or compiler can use the specifications to emit valid CLI images.

This overview will discuss these structures in reverse order, starting with the PE file format, and going down to the layout of the metadata tables in memory.