Too Long; Didn't Read
Blockchain is often presented as a <em>novel way to store data. </em>The data storage is often explained as a<em> </em>distributed ledger<em>. </em>I think this emphasis of the ledger-ness is misleading and hides its potential. In a ledger, the emphasis is on accounting and bookkeeping (see e.g. <a href="http://www.dictionary.com/browse/ledger?r=75&src=ref&ch=dic" target="_blank">this definition</a>). In the following, I will outline how a blockchain do more, in particular store <em>program state</em>, a crucial component for the distributed execution of programs, smart contracts or chain code, and point to current implementations of this idea. A program state is, given a sequence of instructions (think: a recipe), the current instruction we execute, as well as the outcome of all the previously executed instructions (think: taking a snapshot during cooking the recipe).