Basic Question about Mathematica

*To*: mathgroup at smc.vnet.net*Subject*: [mg83369] Basic Question about Mathematica*From*: dmartin19 at gmail.com*Date*: Sun, 18 Nov 2007 04:54:18 -0500 (EST)

I only started using Mathematica yesterday, so please excuse this very newbie question. I was working in a notebook, using help files to try to learn Mathematica. I noticed that Mathematica uses cells for entry, and each of my entries in a cell are tagged by numbers, such as "In[n]" and "Out[n]" where "n" is some number. Being new, I keep making a lot of mistakes while experimenting, and each time when I realize the mistake, I delete the cell and start over again. When I do this, Mathematica does not continue to number the "In[n]" and "Out[n]" lines sequentially based on what is actually on the notebook, but instead remembers the numbers from the deleted cells even after I have deleted them. Consequently, with only 10 or so cells on my notebook, I have numbers like "In[102]" because Mathematica is remembering all the deletions, and all the times I asked it to recalculate. What is worse is that it seems to remember errors and variables from the deleted cells. If I previously made a mistake with some variable or expression and deleted it, then tried to define it again, it gives me the same error I got before I deleted it. Clearing the history does not help. Is there any way to get Mathematica to totally forget stuff that I have deleted and only evaluate whatever is in the notebook at a given time? It would also be great if it could renumber the "In[n]" and "Out[n]" statements so they bear some semblance to the actual number of cells in my notebook. Any help is appreciated!

**Follow-Ups**:**Re: Basic Question about Mathematica***From:*Murray Eisenberg <murray@math.umass.edu>