one they should use and expect. Example encoded in DER Below is the data structure shown above as myQuestion encoded in DER format (all numbers are in hexadecimal): 30 13 02 01 05 16 0e 41 6e 79 62 6f 64 79 20 74 68 65 72 65 3fDER is a type–length–value encoding, so the sequence above can be interpreted, with reference to the standard SEQUENCE, INTEGER, and IA5String types, as follows: 30 — type tag indicating SEQUENCE 13 — length in octets of value that follows 02 — type tag indicating INTEGER 01 — length in octets of value that follows 05 — value (5) 16 — type tag indicating IA5String (IA5 means the full 7-bit ISO 646 set, including variants, but is generally US-ASCII) 0e — length in octets of value that follows 41 6e 79 62 6f 64 79 20 74 68 65 72 65 3f — value ("Anybody there?") Example encoded in XER Alternatively, it is possible to encode the same ASN.1 data structure with XML Encoding Rules (XER) to achieve greater human readability "over the wire". It would then appear as the following 108 octets, (space count includes the spaces used for indentation): <FooQuestion> <trackingNumber>5</trackingNumber> <question>Anybody there?</question> </FooQuestion> Example encoded in PER (unaligned) Alternatively, if Packed Encoding Rules are employed, the following 122 bits (16 octets amount to 128 bits, but here only 122 bits carry information and the last 6 bits are merely padding) will be produced: 01 05 0e 83 bb ce 2d f9 3c a0 e9 a3 2f 2c af c0 In this format, type tags for the required elements are not encoded, so it cannot be parsed without knowing the expected schemas used to encode. Additionally, the bytes for the value of the IA5String are packed using 7-bit units instead of 8-bit units, because the encoder knows that encoding an IA5String byte value requires only 7 bits. However the length bytes are still encoded here, even for the first integer tag 01 (but a PER packer could also omit it if it knows that the allowed value range fits on 8 bits, and it could even compact the single value byte 05 with less than 8 bits, if it knows that allowed values can only fit in a smaller range). The last 6 bits in the encoded PER are padded with null bits in the 6 least significant bits of the