# Initialization (https://docs-kyrm16yq7-ton-core-docs.vercel.app/llms/tvm/initialization/content.md)



## Initialization of `cc`, `cp`, and gas limits [#initialization-of-cc-cp-and-gas-limits]

* The original `cc`, current continuation, is initialized using the cell slice created from the `code` section of the smart contract. If the account is frozen or uninitialized, the code must be provided in the `init` field of the incoming message.

* The `cp`, current TVM codepage, is set to the default value of 0.

* The gas limit values are initialized based on the results of the [credit phase](/llms/foundations/phases/content.md).

## Registers initialization [#registers-initialization]

<Callout type="tip">
  For more info about registers, take a look at [Registers](/llms/tvm/registers/content.md)
</Callout>

* `c0`: `Quit` — extraordinary continuation which terminates TVM with exit code `0`.

* `c1`: `Quit` — extraordinary continuation which terminates TVM with exit code `1`. Both exit codes `0` and `1` are considered successful terminations of TVM.

* `c2`: `ExcQuit` — extraordinary continuation which terminates TVM with an exception. In this case, the exit code is an exception number.

* `c3`: root cell of code currently executing in TVM.

* `c4`: root cell of account data.

* `c5`: empty cell.

* `c7`: `Tuple[Tuple[0x076ef1ea, 0, 0, ...]]`.

## Stack [#stack]

The contents of the stack depend on the event that triggered the transaction:

* Internal message
* External message
* Tick-tock
* Split prepare
* Merge install
* [Get method (off-chain)](/llms/tvm/get-method/content.md)

The top of the stack is always the *function selector*, an *integer* that identifies the event that caused the transaction.

The following function selectors are defined:

| ID | Name              | Description                                        |
| -- | ----------------- | -------------------------------------------------- |
| 0  | onInternalMessage | Received an internal message                       |
| -1 | onExternalMessage | Received an external message                       |
| -2 | onRunTickTock     | Received a tick-tock event                         |
| -3 | onSplitPrepare    | Received a split prepare event (unimplemented yet) |
| -4 | onSplitInstall    | Received a split install event (unimplemented yet) |

Get methods can have arbitrary IDs and should not overlap with the ones listed above.

### External/internal message [#externalinternal-message]

| Index | Name              | Type      | Description                                                                                                                                                   |
| ----- | ----------------- | --------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `s0`  | Function selector | `Integer` | `-1` for external messages, `0` for internal messages.                                                                                                        |
| `s1`  | Message body      | `Slice`   | This is an arbitrary payload of a message, which can be used for text comments (when sending TONs from one wallet to another) or for smart contract commands. |
| `s2`  | Message           | `Cell`    | Cell containing message metadata (sender, receiver, amount) as well as message body.                                                                          |
| `s3`  | Message value     | `Integer` | Amount of received nanotons (`0` for externals).                                                                                                              |
| `s4`  | Contract balance  | `Integer` | Current account balance in nanotons.                                                                                                                          |

### Tick-tock [#tick-tock]

| Index | Name              | Type    | Description                                            |
| ----- | ----------------- | ------- | ------------------------------------------------------ |
| `s0`  | Function selector | Integer | `-2` for tick-tock transactions.                       |
| `s1`  | Tick or tock?     | Integer | `0` for tick transactions, `-1` for tock transactions. |
| `s2`  | Account address   | Integer | 256-bit raw account address (without workchain).       |
| `s3`  | Contract          | Integer | Current account balance in nanotons.                   |

### Split/merge events [#splitmerge-events]

These events are not implemented yet. Possible stack layout for split/merge events is described in [TON Blockchain](/llms/foundations/whitepapers/tblkch/content.md) whitepaper. However, it is subject to change.