--- tags: kba, ncd --- # Scavenger Hunt Challenge `#5` ## What are the different types of Receipts and how do they help dApps scale? This challenge will take you on a tour of cross-contract calls, a distinguishing feature of NEAR Protocol. You will have to read through some documentation and may even end up trying to run some code yourself. Good luck and have fun! --- **Estimates for Time to Complete** - Fastest time: **30 seconds** (if you know exactly where to look) - Most likely time: **10 minutes** - Time to quit: **15+ minutes** (we can help you with some hints in this case) --- **Expected Response Format** - **name:** Firstname Lastname - **email:** you@example.com - **hunt:** 5 - **answer:** _(here the syntax below represents a list of receipt types and explanation)_ - `Type 1`: this is what it does - `Type 2`: this is what it does - here's how these types of receipts work together --- **1. Visit [NEAR U](https://near.org/learn)** `NEAR U` is a great place to start learning about NEAR Protocol. Here you will find several high level explanation of the NEAR platform, examples of dApps currently running on NEAR, workshops, courses and more. **2. Find the `cross-contract calls` workshop** The fastest way to understand what a Receipt is and how they relate to cross-contract calls is this workshop. It is packages as a GitHub repository that you can browse online or clone and use locally. The repo includes several tests to help you get started and is evolving as we speak into a rich explanation of cross-contract calls. **3. Open the document called `README-concepts.md`** This may be best to read online at GitHub since the markdown will be properly formatted for readability. This document explains cross-contract calls in some detail including several examples of how they are used to make your dApps scale with the network. You will find mention of receipts in this document. There are 2 types of Receipts and only one of them is mentioned here. **4. Open the `NEAR nomicon` (specification docs)** NEAR nomicon is the technical specification for NEAR Protocol. You can find it here: https://nomicon.io/RuntimeSpec/Receipts.html This document covers the details of both types of Receipts but will probably not help you understand exactly how they work at a high level ... that's what steps 2 and 3 (above) are for. **5. Format and submit your response** To submit your response to this challenge, compose your answer in the following format: ``` Type 1: this is what it does Type 2: this is what it does here's how these types of receipts work together ``` --- You can learn more about cross-contract calls here: https://docs.near.org/docs/tutorials/how-to-write-contracts-that-talk-to-each-other