Tensors in physics. User’s guide for the Mathematica package CARTAN version 1. 2. Windows, MSDOS, Unix, Linux, VMS, MacOS and OS/2 This book comprises two parts: firstly an introduction to tensor calculus, in particular, the use of tensors in spaces with connection, Riemannian spaces and semi-Riemannian spaces, and in physics, and secondly an introduction to the Mathematica package CARTAN. Contents: 1. Computer algebra, 2. General tensor calculus, 3. Getting started, 4. A reference manual, and 5. Examples. The examples in Chapter 5 give applications in relativity: FLRW cosmology, Kerr metric, a spin-polarized string, vacuum polarization near a planar domain wall, and the Kasner solution.