ISO/IEC 11889 contains the definitions of the Trusted Platform Module (TPM) commands. These commands make use of the constants, flags, structures, and union definitions defined in ISO/IEC 11889-2.

The detailed description of the operation of the commands is written in the C language with extensive comments. The behavior of the C code in this ISO/IEC 11889-3:2015 is normative but does not fully describe the behavior of a TPM. The combination of this ISO/IEC 11889-3:2015 and ISO/IEC 11889-4 is sufficient to fully describe the required behavior of a TPM.

ISO/IEC 11889-3:2015 and ISO/IEC 11889-4 is written to define the behavior of a compliant TPM. In some cases it is not possible to provide a compliant implementation. In those cases, any implementation provided by the vendor that meets the general description of the function provided in this part of ISO/IEC 11889 would be compliant.