Where does the name Motoko comes from ?

A reference to Satoshi Nakamoto

It comes from Ghost in the shell.

Motoko is the second name of Andreas Rossberg, one of the architect of the Motoko language.

What is a stable variable in Motoko ?

Once you assign a value to it, you can't reassign a new value.

It is necessary a variable of type : Nat or Int or Bool.

It is a variable which state is preserved accross updates.

What is the freezing threshold of a canister?

The amount of requests that a single canister can process.

The amount of CPU power allocated to a canister, that cannot be depassed or the canister will trap.

The minimum number of seconds a canister must be able to sustain itself given the canister’s current size and the system’s current cost for storage.

How can any user check the authenticity of the code inside a canister ?

Using hash of the Wasm module inside a canister which is available through a public call.

On the Internet Computer every code of every canister is transparent and public : you can check it.

This is not possible for the moment.

Is there a link between the principal of a user and his public key ?

They are not related.

The principal is the result of SHA256(Public Key).

The principal is the result of SHA224(Public Key).

What are cycles ?

The number of instructions a canister can process in one second.

A currency used to pay calculation and storage on the IC.

The number of ICP staked inside a neuron.

How does the Internet Identity work ?

You delegate a short-term key session to an identity service provider built on top of the Internet Computer that will then connect to others applications and delegate again to each application a new session key.

It keeps a list of all the services you use and all the identifiants for those services.

It creates a single identity that all canisters can use freely, assuring full interopability between canisters.

What is one amazing feature of the IC possible because of ChainKey ?

The use of any language that compile to Wasm to create a canister module.

The speed at which query call are executed.

One public key for the whole Internet Computer, which means you can easily authenticate any message coming from the IC.

What are catch-up packages ?

A feature that allows a canister to copy the state of another canister to help him scale.

The state of a subnet that you can give to a new node to join this subnet at anypoint.

The system of package management in Motoko.

Are the blocks in any subnet stored forever ?

No and that's a main reason why the IC is far ahead in terms of cost of file storage relatively to any other blockhain out there.

Of course they are, all blocks are linked to the previous one so you can't erase one without destroying the blockchain.

For the NNS they are stored forever, for other applications they are not.

Motoko School © 2021

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Internet Computer : Quizz number 2 ! 👨‍🏫