Question: In EE all we need to draw some waveforms to ask or answer questions.

Is this could be done with TeX? Or what are the software's you people are using?

Could we have add some tools to draw waveforms in here?

Answer: 
Software I have on my laptop that can be used for this purpose includes: LTSpice, Scilab, Maxima, Inkscape - which has a nice function generator addin which can be used for quite complex waveforms, you just use a mathematical expression. It's under `Extensions->Render->Function Plotter`

![Inkscape Function Plotter](https://i.stack.imgur.com/OA384.png)

Math Functions Available:

![Inkscape Function Plotter Math Functions](https://i.stack.imgur.com/S95Qb.png)
Some timing diagram answers were listed [in this question](https://electronics.stackexchange.com/questions/3564/software-to-create-timing-diagrams). [TimingDesigner](http://www.timingdesigner.com/Docs/TD_datasheet.pdf) and [TimeGen](http://www.xfusionsoftware.com/purchase_timegen.html) were mentioned. Another is TimingDiagramer.