Welcome to this 20-article series to master Claude Code! Each day, we’ll explore a feature that will make you a more efficient developer. Today: installation and first steps.
What is Claude Code?
Claude Code is Anthropic’s official command-line interface for interacting with Claude. Unlike traditional web chatbots, Claude Code integrates directly into your terminal and understands your codebase.
What sets it apart:
- Direct access to your files and terminal
- Understanding of your project context
- Ability to read, write, and execute code
- Native Git integration
Installation
Prerequisites
- Node.js 18+ installed (or Bun as an alternative)
- An Anthropic account (API or claude.ai)
Installation via npm
npm install -g @anthropic-ai/claude-code
First Authentication
claude
On first run, Claude Code will guide you through the login process. Two options:
- claude.ai account: Billing based on your subscription
- Anthropic API: Token-based billing (~$6/day on average)
Your credentials are stored locally—no need to reconnect each session.
The CLAUDE.md File: Your Contract with the AI
The first thing to do after installation: create a CLAUDE.md file at your project root.
# CLAUDE.md
## Project Context
E-commerce application in Next.js 14 with strict TypeScript.
## Conventions
- Use Server Components by default
- Tests with Vitest
- [Conventional commits](/en/conventional-commits-standardize-git-messages-optimized-collaboration/) (feat:, fix:, etc.)
## Useful Commands
- `npm run dev`: Development server
- `npm run test`: Run tests
- `npm run lint`: Code verification
Claude automatically reads this file and adapts its responses to your context. It’s your contract with the AI: the more precise it is, the more relevant Claude will be.
Essential Commands
Navigation Commands
| Command | Action |
|---|---|
/help |
Display complete help |
/clear |
Clear conversation history |
/exit or Ctrl+D |
Exit Claude Code |
Diagnostic Commands
| Command | Action |
|---|---|
/doctor |
Check system health |
/config |
View/modify configuration |
/model |
Change model (Haiku/Sonnet/Opus) |
Session Commands
| Command | Action |
|---|---|
/cost |
View current session cost |
/compact |
Reduce context size |
Example Session
$ claude
╭─────────────────────────────────────╮
│ Claude Code │
│ Model: claude-sonnet-4-5-20250929 │
╰─────────────────────────────────────╯
> Explain this project's structure
I'll analyze your project structure...
[Claude reads files and responds with context]
Essential Keyboard Shortcuts
| Shortcut | Action |
|---|---|
Ctrl+C |
Cancel current operation |
Ctrl+L |
Clear terminal screen |
Ctrl+D |
Exit Claude Code |
Tab |
Toggle extended thinking |
Esc Esc |
Go back (rewind) |
Ctrl+R |
Search history |
Choosing the Right Model
Claude Code offers three models with different trade-offs:
| Model | Strength | Cost | Recommended Use |
|---|---|---|---|
| Haiku | Fast, economical | $ | Simple questions, quick exploration |
| Sonnet | Balanced | $$ | Daily use, most tasks |
| Opus | Maximum capability | $$$ | Complex problems, architecture |
To change models:
/model haiku
/model sonnet
/model opus
First Practical Exercise
Try these commands in one of your projects:
# 1. Launch Claude Code
claude
# 2. Request an analysis
> Describe this project's structure and identify the technologies used
# 3. Check the cost
/cost
# 4. Switch to a lighter model for a simple question
/model haiku
> What is the application's entry point?
# 5. Switch back to Sonnet
/model sonnet
Best Practices from the Start
- Always create a CLAUDE.md: Even minimal, it drastically improves responses
- Use
/clearbetween tasks: Avoids context pollution - Start with Sonnet: Best quality/cost ratio for beginners
- Check
/costregularly: Get into the habit of monitoring your consumption
What’s Coming Tomorrow
In Day 2, we’ll discover Claude Code’s secret syntax: the #@/! shortcuts that make the difference between a basic user and a power user.
This article is part of the “Master Claude Code in 20 Days” series. Find all articles on my blog.
📚 Related Articles
