Identifiers (G.3.3)

(6.1.2) The number of significant initial characters (beyond 31) in an identifier without external linkage:

The first 1,023 characters are significant. Identifiers are case-sensitive.

(6.1.2) The number of significant initial characters (beyond 6) in an identifier with external linkage:

The first 1,023 characters are significant. Identifiers are case-sensitive.