The identifier, or tag, is encoded as one or more octets as shown in
Figure 
. It gives the type of the data specified in the
content component. In a single-octet identifier, bits 8 and 7 represent a class
(UNIVERSAL is 00, APPLICATION is 01, CONTEXT-SPECIFIC is 10, and
PRIVATE is 11), bit 6 specifies the data element as primitive
(0) or structured (1), and bits 5 through 1 give the tag number.
For example, 00000011 indicates that the tag class is UNIVERSAL (00),
the data element is primitive (0), and the tag number is 3 (00011),
the BIT STRING tag number.
Figure: Identifier (Tag) encoding
More than five bits, hence additional octets, are required when the tag number is greater than 31. In that case, bits 5 through 1 of the first octet are 1 and each remaining octet has a 1 or 0 in bit 8, depending on whether the tag number is continued in at least one or no octet, respectively. For example, the tag APPLICATION 293 is encoded as 01111111 10000010 00100101.