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Claude Code Basics

Claude Code is Anthropic's official CLI tool for AI-assisted software development. It runs in your terminal and has direct access to your filesystem, allowing it to read, write, and execute code.

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explain

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Getting Started​

Installation​

# Install via npm
npm install -g @anthropic-ai/claude-code

# Or via Homebrew
brew install claude-code

Starting a Session​

# Start in current directory
claude

# Start in a specific directory
claude /path/to/project

# Resume a previous conversation
claude --continue

Core Interaction Model​

Claude Code operates through a conversational interface. You type natural language requests, and Claude responds by:

  1. Analyzing your request
  2. Using tools to accomplish tasks (reading files, running commands, etc.)
  3. Responding with results and explanations

Example Interaction​

Try it: See how Claude reads and modifies files.

claude

   ╭─────────────────────────────────╮
   │                                 │
   │   ██████╗██╗      █████╗ ██╗   │
   │  ██╔════╝██║     ██╔══██╗██║   │
   │  ██║     ██║     ███████║██║   │
   │  ██║     ██║     ██╔══██║██║   │
   │  ╚██████╗███████╗██║  ██║██║   │
   │   ╚═════╝╚══════╝╚═╝  ╚═╝╚═╝   │
   │                                 │
   │         claude code             │
   │                                 │
   ╰─────────────────────────────────╯

Key Concepts​

1. Context Awareness​

Claude Code reads your project's structure and understands:

  • File contents and relationships
  • Code patterns and conventions
  • Project configuration (package.json, build files, etc.)
  • Git history and status

2. CLAUDE.md Files​

You can create a CLAUDE.md file in your project root to give Claude persistent instructions:

# CLAUDE.md

## Project Overview
This is a Node.js API using Express...

## Conventions
- Use async/await, not callbacks
- Tests go in __tests__ directories
- Use TypeScript strict mode

## Commands
- npm test: Run tests
- npm run build: Build project

Claude reads this file automatically and follows your guidelines.

3. Tool Usage​

Claude has access to specialized tools:

  • Read: Read file contents
  • Write: Create new files
  • Edit: Modify existing files
  • Bash: Run shell commands
  • Glob: Find files by pattern
  • Grep: Search file contents
  • WebSearch/WebFetch: Access web information
  • Task: Spawn specialized sub-agents

4. Permission Model​

Claude asks for permission before:

  • Running potentially destructive commands
  • Making significant file changes
  • Accessing external resources

You can pre-approve common operations to streamline your workflow.

Built-in Commands​

Type these directly in the CLI:

CommandDescription
/helpShow help and available commands
/clearClear conversation history
/compactSummarize and compact the conversation
/statusShow current session status
/costDisplay token usage and costs
/tasksList running background tasks

Session Management​

Conversation Continuity​

Claude maintains context throughout your session. You can:

  • Reference earlier parts of the conversation
  • Build on previous work
  • Ask follow-up questions

Automatic Summarization​

Long conversations are automatically summarized to maintain context while managing token limits.

Interactive: Your First Session​

Try this interactive terminal to experience Claude Code:

First Session
beginner
📁 my-project/
📄 ├── package.json
📁 ├── src/
📄 └── README.md
*Initialized. No CLAUDE.md found.*
>
💡Claude can explore your project even without CLAUDE.md. Try asking about the codebase.

Interactive: Essential Commands​

Learn the built-in commands that help manage your session:

Essential Commands
beginner
📁 my-project/
📄 └── CLAUDE.md✓
*Initialized. Found CLAUDE.md.*
>
💡These commands give you visibility into your session state.