LibreCAD is one of the best options if you want to design a plan or simply put into practice your basic or professional architecture knowledge, all for free and with a quite simplified interface. As with major design programs, with this software you can draw, dimension, modify, consult, search, measure, and of course print, considering each of the parameters of your design in detail. In the drawing section, LibreCAD offers its greatest qualities, given that the interface is so simple that anyone with basic knowledge can create a design in a few minutes. In this sense, the menu unfolds very simply, with shapes and figures on the left side and layers on the right side, as you create and organize them. This is a great help, as it is not necessary to write commands or search through multiple menus for drawing options.

GNU Octave is the free alternative of MATLAB. It provides support to all the matlab commands and on the same time it is open source,light weight, and best for developers working at home

Emacs is basically a fully programming language with a build in text editor, customizable to the bones; itself emacs has one of the most loyal and active community on the free software world