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To my novice understanding the blockchain is stored on all participating computers in the network. Is this to say each computer has the entire chain downloaded onto the hard drive? Or do we merely query the chain from designated nodes? More specifically if I download Daedalus Main net or some other node software will the entire blockchain be stored and constantly updating eating up my memory little by little?

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[...] each computer has the entire chain downloaded onto the hard drive? Or do we merely query the chain from designated nodes?

Full-nodes (a node is a wallet etc) typically store a full copy of the transaction journal (blockchain) locally in non-volatile storage - typically a hard-disk. Not in memory (RAM).

Pruning nodes discard transaction data that has been processed and that they no longer need - this greatly reduces their storage needs. It does slightly hamper other new full-nodes processing the full transaction journal - they have to find other, non-pruning, sources for pruned blocks. They need to do this to independently and trustlessly determine the current state (the set of monetary amounts valid for use as inputs in future transactions)

Lightweight nodes, mostly those that use Simplified Payment Verification (SPV), trust other nodes to store the full transaction journal. They don't store a permanent local copy of the transaction journal to any significant extent.

In future it may be that, in the next 100 years, SPV nodes will predominate or that non-volatile storage will be smaller, cheaper and higher capacity, or that changes to the network protocols etc will address this in novel ways.

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Suppose crypto is adopted globally, and 100 years pass. Where would 100 years worth of global transactions/smart contracts be stored?

In persistent storage space. The same as now. For Bitcoin particularly, the main chain doesn't grow faster than ~50GB a year, quite sustainable compared to alternative chains with larger maximum throughput, such as the Wright hard fork.

To my novice understanding the blockchain is stored on all participating computers in the network.

Yes. Except any node catching up, and synced pruned nodes.

is this to say each computer has the entire chain downloaded onto the hard drive?

Full nodes have the entire chain in persistent storage, or they are catching up. In theory, they are always catching up, but if the last known good block is young, you could say "it is mostly up to date". You can never know if a new valid block was just mined somewhere.

Pruned nodes start removing old blocks from persistent storage when they reach their target storage use, whatever the number is, e.g. prune every block except last 2GB of block data.

Or do we merely query the chain from designated nodes?

Yes, too. As needed.

More specifically if i download Daedalus Main net or some other node software will the entire blockchain be stored and constantly updating eating up my memory little by little?

If you download a full node software, yes it'll keep eating up your storage space. If you download a pruned node software, it will not.

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  • OP is not asking Bitcoin. Dec 12 '21 at 17:20
  • Edited, thanks.
    – Mercedes
    Dec 12 '21 at 19:10

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