# rawstate
## Manually Maintain Mutable State
One way to implement state in contract is dividing the contract in the locking script into two parts: data and code. Data part is the state. Code part contains the business logic of a contract that encodes rules for state transition.
sCrypt offers [stateful contracts](https://medium.com/xiaohuiliu/stateful-smart-contracts-on-bitcoin-sv-c24f83a0f783). Let us look at a simple example of a stateful contract: a counter contract tracking how many times its function `increment()` has been called. Its code is shown below with comments inline.
```javascript
contract Counter {
public function increment(SigHashPreimage txPreimage, int amount) {
require(Tx.checkPreimage(txPreimage));
// deserialize state (i.e., counter value)
bytes scriptCode = Util.scriptCode(txPreimage);
int scriptLen = len(scriptCode);
// counter is at the end
int counter = unpack(scriptCode[scriptLen - Util.DataLen :]);
// increment counter
counter++;
// serialize state
bytes outputScript = scriptCode[: scriptLen - Util.DataLen] + num2bin(counter, Util.DataLen);
bytes output = Util.buildOutput(outputScript, amount);
// ensure output is expected: amount is same with specified
// also output script is the same with scriptCode except counter incremented
require(hash256(output) == Util.hashOutputs(txPreimage));
}
}
```
`OP_RETURN` data of the contract locking script can be accessed by using an accessor named `dataPart`, for example:
```typescript
const Counter = buildContractClass(loadDescription('counter_desc.json'));
counter = new Counter();
const dataPart = counter.dataPart;
const dataPartASM = counter.dataPart.toASM();
const dataPartHex = counter.dataPart.toHex();
// to set it using ASM
counter.setDataPart('01');
```
After that, the `counter.lockingScript` would include the data part automatically. You can use it to calculate preimage.
```typescript
const preimage = getPreimage(tx, counter.lockingScript, inputSatoshis)
```
If you want to access the code part of the contract's locking script including the trailing `OP_RETURN`, use:
```typescript
const codePart = instance.codePart;
const codePartASM = instance.codePart.toASM();
const codePartHex = instance.codePart.toHex();
```
---
# Agent Instructions: Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.
Perform an HTTP GET request on the current page URL with the `ask` query parameter:
```
GET https://radiantblockchain.gitbook.io/wiki/programming/scryptlib/rawstate.md?ask=
```
The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.
Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.