> For the complete documentation index, see [llms.txt](https://yutian-chen.gitbook.io/c0vm.ts-dev-documentation/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://yutian-chen.gitbook.io/c0vm.ts-dev-documentation/vm-core/parsing/bc0-file-parser.md).

# BC0 File Parser

A `bc0` file is divided into several sections:

1. **Magic Number**\
   Starting with `C0 C0 FF EE`, the magic number tells us that this file is generated by a `CC0` compiler. Some other "meta-data" like version number etc. are also included in this section.
2. **Integer Pool**\
   Inside the `bc0` instructions, we can push small values ranging from `0x00` to `0xFF` directly into the operand stack using `BIPUSH` instruction. However, to use larger integer constants (literals that written in the code like `0xDEADBEEF`), we need to store them separately in a **Int Pool**.
3. **String Pool**\
   String literals are stored in a specific memory section and will be loaded when the VM initializes. During the runtime, these strings will be loaded into the operand stack according to the instructions. This specific section is called the **String Pool**.
4. **Functions**\
   The name of function and the bytecode instructions.
5. **Native Pool**\
   The native functions that will be needed in this program will be logged here.

The parser will convert the `bc0` raw string into a data structure like this:

```typescript
type C0ByteCode = {
    version: number;
    /* Int Constant Pool */
    intCount: number;
    intPool: Int32Array;
    /* String Constant Pool */
    stringCount: number;
    stringPool: Uint8Array;
    /* Function Pool */
    functionCount: number;
    functionPool: C0Function[];
    /* Native Functions */
    nativeCount: number;
    nativePool: (C0Native|undefined)[];
};
```