Introduction to Claude Code

Claude Code is an agentic coding tool made by Anthropic that lives in your terminal. It can understand your codebase, make edits across multiple files, run commands, and help you work faster as a developer. Think of it as a senior developer pair-programmer that never gets tired.

What Can Claude Code Do?

Edit files – Create, modify, and refactor code across your project
Run commands – Execute shell commands, run tests, manage git
Search codebases – Find files, grep for patterns, understand architecture
Debug issues – Analyze errors, trace bugs, suggest fixes
Answer questions – Explain code, suggest approaches, teach concepts

Prerequisites

Node.js 18 or later
An Anthropic API key (or a Claude Pro/Max subscription)
A terminal (macOS, Linux, or WSL on Windows)

Installation

Install Claude Code globally using npm:

npm install -g @anthropic-ai/claude-code

Verify the installation:

claude --version

First-Time Setup

Navigate to any project directory and launch Claude Code:

cd my-project
claude

On first launch, Claude Code will:

Ask you to authenticate (either via API key or OAuth with your Anthropic account)
Request permission to access your project directory
Present you with an interactive terminal prompt

Authentication Options

Option 1: Anthropic API Key

Set your API key as an environment variable:

export ANTHROPIC_API_KEY="sk-ant-your-key-here"

Option 2: Claude Pro/Max Subscription

If you have a Claude Pro or Max subscription, Claude Code will open a browser window for OAuth authentication. This is the easiest option if you already have a subscription.

Configuration

Claude Code stores its configuration in ~/.claude/. Key settings can be configured via:

# View current settings
claude config list

# Set a configuration value
claude config set theme dark

Quick Test

Let’s verify everything works. In your project directory, run:

claude "What files are in this directory?"

Claude Code should list the files in your current directory, confirming it can read your filesystem and respond to queries.

Summary

You now have Claude Code installed and configured. In the next tutorial, we’ll learn how to have effective conversations with Claude Code to get the most out of it.

Next: Your First Conversation with Claude Code