[{$pagename}] ([PER]) are [ASN.1] [encoding] rules for producing a compact transfer syntax for data structures described in [ASN.1], defined in [1994|Year 1994]. 

[{$pagename}] provides a much more compact [encoding] than [Basic Encoding Rules] as [{$pagename}] uses additional information, such as the lower and upper limits for numeric values, from the [ASN.1] specification to represent the data units using the minimum number of bits. 

The compactness requires that the decoder knows the complete abstract syntax of the data structure to be decoded. 

!! unaligned and aligned 
There are two variations of packed encoding rules unaligned and aligned. 
* unaligned [encoding] - the [bits] are packed with no regard for octet (byte) boundaries. 
* aligned [encoding] - certain types of data structures are aligned on [octet] boundaries, meaning there may be some number of wasted [padding bit]s. Unaligned encoding uses the least number of bits, but presumably at some cost in processing time. 

[{$pagename}] also define a restricted set of [encoding] rules, called CANONICAL-PER, which is intended to produce only a single possible encoding for any given data structure. CANONICAL-PER's role is therefore similar to the role of [Distinguished Encoding Rules] or [Canonical Encoding Rules]. 

!! More Information 
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[{ReferringPagesPlugin before='*' after='\n' }]