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};
Every smart contract has an [address](/foundations/addresses/overview) used for all on-chain interactions.
Tolk provides the following types for working with addresses:
* `address` — a standard address; also called "internal address".
* `address?` — nullable address, i.e., either a standard address or `null`; also called "internal or none".
* `any_address` — any kind of address, including external addresses.
## Components
A standard, internal `address` consists of:
* a `int8` workchain — currently, there are only two: masterchain (-1) and basechain (0);
* a `uint256` hash — a 256-bit account ID.
`address` has methods to retrieve these components:
```tolk theme={"theme":{"light":"github-light-default","dark":"dark-plus"},"languages":{"custom":["/resources/grammars/tolk.tmLanguage.json","/resources/grammars/tlb.tmLanguage.json","/resources/grammars/fift.tmLanguage.json","/resources/grammars/tasm.tmLanguage.json","/resources/grammars/func.tmLanguage.json"]}}
fun checkAddress(addr: address, expectHash: uint256) {
val (wc, hash) = addr.getWorkchainAndHash();
assert (wc == 0) throw 123;
assert (hash == expectHash) throw 456;
}
```
When [serialized](/languages/tolk/types/overall-serialization), values of `address` type occupy 267 bits:
* 3 bits for the standard address prefix — `0b100`
* 8-bit workchain
* 256-bit hash
During deserialization from a cell, the values of type `address` are automatically validated at runtime: if parsing succeeds, the resulting address is guaranteed to be valid.
## Comparison
Compare addresses using `==` or `!=`. Internally, an [address is represented as a raw `slice` without references](/languages/tolk/types/overall-tvm-stack), so `==` and `!=` test for bits equality.
```tolk theme={"theme":{"light":"github-light-default","dark":"dark-plus"},"languages":{"custom":["/resources/grammars/tolk.tmLanguage.json","/resources/grammars/tlb.tmLanguage.json","/resources/grammars/fift.tmLanguage.json","/resources/grammars/tasm.tmLanguage.json","/resources/grammars/func.tmLanguage.json"]}}
struct Storage {
owner: address
// ...
}
fun onInternalMessage(in: InMessage) {
var st = Storage.load();
// process a message only from owner
if (in.senderAddress == st.owner) {
// ...
}
}
```
## Embedding
Embed a constant value of type `address` using the `address()` function:
```tolk theme={"theme":{"light":"github-light-default","dark":"dark-plus"},"languages":{"custom":["/resources/grammars/tolk.tmLanguage.json","/resources/grammars/tlb.tmLanguage.json","/resources/grammars/fift.tmLanguage.json","/resources/grammars/tasm.tmLanguage.json","/resources/grammars/func.tmLanguage.json"]}}
const REFUND_ADDR = address("EQCRDM9h4k3UJdOePPuyX40mCgA4vxge5Dc5vjBR8djbEKC5")
```
## Nullable address
A nullable address often represents a potentially absent value:
* There might be an `adminAddress` in the contract's storage, but it may be unset.
* There might be an `sendExcessesTo` field in a message: if exists, send surplus there; if not, keep it.
Thus, type `address?` represents a "none address": either an internal address or none. Check for `null` before usage:
```tolk theme={"theme":{"light":"github-light-default","dark":"dark-plus"},"languages":{"custom":["/resources/grammars/tolk.tmLanguage.json","/resources/grammars/tlb.tmLanguage.json","/resources/grammars/fift.tmLanguage.json","/resources/grammars/tasm.tmLanguage.json","/resources/grammars/func.tmLanguage.json"]}}
// May have no admin
fun send(adminAddress: address?) {
if (adminAddress == null) {
return;
}
// send a message to adminAddress, it's not null
}
```
When a value of type `address?` is serialized and is not `null`, it occupies 267 as the standard `address`. If it is `null`, then it occupies only 2 zero bits, a so-called `addr_none`.
The "none" address can be created using `createAddressNone()`.
## Any address
All external messages from outside world to blockchain contracts, such as wallet contracts, come from external addresses.
To represent internal and external addresses, as well as nullable addresses, use `any_address`:
```tolk theme={"theme":{"light":"github-light-default","dark":"dark-plus"},"languages":{"custom":["/resources/grammars/tolk.tmLanguage.json","/resources/grammars/tlb.tmLanguage.json","/resources/grammars/fift.tmLanguage.json","/resources/grammars/tasm.tmLanguage.json","/resources/grammars/func.tmLanguage.json"]}}
struct CrossBridgeMessage {
destination: any_address
}
```
## Casts
To manually operate on the bits of an `address`, cast it to a `slice`:
```tolk theme={"theme":{"light":"github-light-default","dark":"dark-plus"},"languages":{"custom":["/resources/grammars/tolk.tmLanguage.json","/resources/grammars/tlb.tmLanguage.json","/resources/grammars/fift.tmLanguage.json","/resources/grammars/tasm.tmLanguage.json","/resources/grammars/func.tmLanguage.json"]}}
val s = someAddr as slice;
s.loadUint(3); // 0b100 — internal address tag
s.loadInt(8); // workchain
```
Since an address is represented as a `slice` at the TVM level, such cast is permitted and is safe. Conversely, the cast in another direction is **unsafe**, because no validation is performed at runtime and any further use might fail:
```tolk theme={"theme":{"light":"github-light-default","dark":"dark-plus"},"languages":{"custom":["/resources/grammars/tolk.tmLanguage.json","/resources/grammars/tlb.tmLanguage.json","/resources/grammars/fift.tmLanguage.json","/resources/grammars/tasm.tmLanguage.json","/resources/grammars/func.tmLanguage.json"]}}
var b = beginCell()
.storeUint(0b01) // addr_extern
...;
var s = b.endCell().beginParse();
return s as any_address;
```