IFEFFIT is a command-based program. That is, you tell IFEFFIT to do something, it does that and then waits for you to tell it what to do next. The commands that IFEFFIT accepts are simple statements (there are no loops or conditional statements) useful for data manipulation, and especially for XAFS analysis. Most commands tell IFEFFIT to manipulate arrays of numerical data. There are commands for reading arrays from files, writing arrays to files, plotting arrays, doing simple mathematical manipulation of arrays, and more XAFS-specific commands such as background-spline removal and Fourier transforms. It can also fit XAFS data using theoretical standards from FEFF with complex modeling abilities and automated error analysis. This chapter gives a quick overview of IFEFFIT with a simple annotated example. Much of this material is also covered in The IFEFFIT Tutorial.