A system has been created as an instrument to implement the facilities provided in ISO 2022 for invoking several sets at code extension, to identify each available set, and to present the whole of these sets in a list, with the full specifications of every member: the International Register of Coded Character Sets to be Used with Escape Sequences. In this register, there is specified for each invokable set, a number, the codetable, a list of all characters included together with their full name, and the Final Byte of the Escape Sequence. Individual registered sets are identified as ISO-IR, followed by a number. Additions to the Register may be proposed by a Sponsoring Body, that is a National Body or a Liaison Body. The rules of the game are specified in ISO 2375. It must be pointed out that a codetable, that once has been assigned a number, never can be changed, variants receive a new number. All C or G sets, that are included in any standard from SC2, are always the subject of registration. Apart from these, a number of sets of more limited significance is incorporated. All applications for registration are being submitted for comment to SC2 first. But SC2 cannot apply modifications. The register can be ordered from ECMA, that acts as Registration Authority.

It may seem to outsiders that at receiving the Register a world will open to them of unknown scripts. But the content will disappoint them. Apart from the well-known codetables from the standards, not much more than some 7-bit national versions figure in the list and variants thereof. Only the Chinese and Japanese table present something new. The highest number is now 182. The importance of the register is in the first place based on the unique number by which a C or G set always can be identified, and through which only a single letter's difference results in a separate registration. A prominent example is that of ASCII that has for identification ISO-IR 6, whilst the old ISO 646 IRV has ISO-IR 2, because it contains instead of a DOLLAR SIGN a CURRENCY SIGN.

Because an Escape Sequence requires identification of the C or G set, registration of tables without such a structure is in principle not possible, unless a Final Byte indicates that it is a code outside the ISO 2022 system. This way out has hardly ever been applied, apart from ISO 10646, quite recently. EBCDIC or PC-codes are not registered. At indicating the selected coding in network-protocols this missing facility causes a problem.