For a block that may be designated for implementation in either software or hardware, the block may have a specification in block specifications 504 that is either a specification in a general purpose programming language or {HEAD ~ a specification} in {TAIL ~ a hardware description language} 
For a block that may be designated for implementation in either software or hardware , the block may have a specification in block specifications 504 that is either a specification in a general purpose programming language or { HEAD ~ a specification } in { TAIL ~ a hardware description language }
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