> ## Documentation Index > Fetch the complete documentation index at: https://docs.ton.org/llms.txt > Use this file to discover all available pages before exploring further. ## Submitting Feedback If you encounter incorrect, outdated, or confusing documentation on this page, submit feedback: POST https://docs.ton.org/feedback ```json { "path": "/tvm/builders-and-slices", "feedback": "Description of the issue" } ``` Only submit feedback when you have something specific and actionable to report. # Builders and Slices In TVM, the `Cell` type contains only metadata of the cell: level, hashes, and depths. To read actual data, TVM need to *load* cell from celldb, key-value storage of the node, which stores cells by their representation hashes. [`CTOS`](/tvm/instructions#d0-ctos) instruction loads a cell by its metadata from `Cell` type, and provides a `Slice`, a read-only wrapper for the cell's content. To simplify coding cell deserializers in smart contracts, instead of behaving like a simple bit/ref array, `Slice` is a "read cursor": it allows loading a piece of data from the beginning of the slice, returning that data and the slice that contains remaining data. On the other hand, there is a `Builder` type, which provides a convenient way to serialize data to a cell. Only the `Cell` type can be used outside of TVM: in output actions and in persistent storage. ## Builder Builder provides a way to construct a cell from a sequence of values of the following TVM types: integers, cells (as references), slices, and builders. Tuples, continuations, and `null` are not serializable. For example, serialize the following numbers to a cell: ``` 1 (uint4) 2 (uint4) -1 (int8) ``` First, create an empty builder using [`NEWC`](/tvm/instructions#c8-newc): ```fift Fift 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"]}} NEWC // returns empty builder x{} ``` Then, put a number on the stack: ```fift Fift 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"]}} 1 INT // stack: x{} 1 ``` And call [`STU`](/tvm/instructions#cb-stu) ("STore Unsigned integer") to store integer into builder (swapping builder and value to meet `STU` input order): ```fift Fift 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"]}} SWAP // stack: 1 x{} 4 STU // stack: x{0001} ``` Then, store the other two numbers: ```fift Fift 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"]}} 2 INT // x{0001} 2 SWAP // 2 x{0001} 4 STU // x{00010010} -1 INT // x{00010010} -1 SWAP // -1 x{00010010} 8 STI // x{0001001011111111} ``` And, finally, [`ENDC`](/tvm/instructions#c9-endc) instruction finalizes the builder to a cell. ## Slice Slice allows reading data back from a cell, field by field. For example, deserialize bitstring `x{0001001011111111}` created above. [`CTOS`](/tvm/instructions#d0-ctos) ("Cell TO Slice") loads a `Cell` to a `Slice`. ```fift Fift 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"]}} // assume a cell with bitstring x{0001001011111111} is on the stack CTOS // x{0001001011111111} ``` Then, call [`LDU`](/tvm/instructions#d3-ldu) ("LoaD Unsigned integer") to read first value (`uint4`). ```fift Fift 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"]}} 4 LDU // 1 x{001011111111} ``` `LDU` takes the first 4 bits from a slice and creates a new slice without these 4 bits: `x{0001|001011111111}` slices into a number `0001` and a slice `x{001011111111}`. Similarly, read another two numbers: ```fift Fift 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"]}} 4 LDU // 1 2 x{11111111} 8 LDI // 1 2 -1 x{} ``` A common way to ensure there is no data left inside the slice is to call [`ENDS`](/tvm/instructions#d1-ends).