• Introduction
• Theory Notes
  • Internet Computer
  • DFX
• Features and Functionality
• Implementation
  • Backend Code
  • Frontend Code
• Running the Project Locally

D-Ledger is a decentralized application (dApp) created to learn and demonstrate the capabilities of the Internet Computer (IC) blockchain. This application simulates a simple banking system where users can top-up, withdraw, and check their balance.

The Internet Computer is a blockchain that runs at web speed with unbounded capacity. It aims to extend the functionality of the public internet so that it can host backend software, transforming it into a global compute platform. Key features include:

• Canisters: Smart contracts on the Internet Computer that combine code and state.
• Cycles: The fuel that powers computation in the Internet Computer.
• Motoko: A programming language designed for the Internet Computer.

DFX is the command-line tool used to manage, deploy, and interact with canisters on the Internet Computer. Key commands include:

• dfx start: Starts the local replica.
• dfx new <project-name>: Creates a new project.
• dfx deploy: Deploys the canisters.
• dfx canister call <canister-name> <method-name>: Calls a method on a canister.

To learn more before you start working with dbank2, see the following documentation available online:

• Quick Start
• SDK Developer Tools
• Motoko Programming Language Guide
• Motoko Language Quick Reference

• Top-Up: Allows users to add funds to their account.
• Withdraw: Enables users to withdraw funds from their account, ensuring the balance does not go negative.
• Check Balance: Users can query their current balance at any time.
• Compound Interest: The balance compounds over time, simulating interest accrual.

The backend canister is written in Motoko and manages the core banking operations: topping up, withdrawing, checking the balance, and compounding interest.

The frontend is a simple HTML page with a form for user interactions and JavaScript for handling user input and communicating with the backend.

If you want to test your project locally, you can use the following commands:

• Starts the replica, running in the background

dfx start --background

• Deploys your canisters to the replica and generates your candid interface

dfx deploy

• If you have made changes to your backend canister, you can generate a new candid interface with

npm run generate

at any time. This is recommended before starting the frontend development server, and will be run automatically any time you run dfx deploy

• Start a development server with

npm start

Which will start a server at http://localhost:8080, proxying API requests to the replica at port 4943.

npm start

Which will start a server at http://localhost:8080, proxying API requests to the replica at port 4943.