Chapter 1, Getting Started with the Robot Operating System

1. Here are the three main features of ROS:
   • Message passing interface to communicate with different programs
   • Off-the-shelf robotics algorithm to make the robot prototyping faster
   • Software tools to visualize robot data and debugging
2. The different levels of concepts in ROS are the ROS Filesystem level, ROS Computation Graph Level, and ROS Community Level.
3. The Catkin build system is built using CMake and Python scripts. This tool helps us build the ROS packages.
4. The ROS topic is a named bus in which one node can communicate to another node. The kind of message type used in the topics are ROS messages.
5. The different concepts of the ROS computation graph are ROS Nodes, ROS Topics, ROS Messages, ROS Master, ROS Services, and ROS Bags.
6. The ROS Master act as a mediator program to connect two ROS nodes to start communicating with each other.
7. The important features of Gazebo are:
   • Dynamic simulation: It includes physics engine like ODE, Bullet, Simbody and Dart
   • Advanced 3D graphics: It uses OGRE framework to create high-quality lighting, shadows, and textures
   • Plugin support: This will allow developers to add new robot, sensors, and environmental control
   • TCP/IP Transport: Controlling Gazebo using socket-based message passing interface