How to program a probabilty plot?

I am trying to write a little code to make a probability plot. I don't think it will take much effort once I have the right recipe. I think I have found the algorithm here.

http://www.itl.nist.gov/div898/handbook/eda/section3/normprpl.htm

There are a couple of things I am not sure about. The "uniform order statistic medians" are first called U(i). Then, when defined, they are called m(i) as far as I can tell. Have they just switched the symbol from U to m or is there something I am missing? Apparently, I am supposed to know what the "ordered response values" are because I can find a number of references to them via Google, but nowhere can I find a definition. What are they? Also, I have found two methods for making probability plots. One is as in the link above. The other, which I can't find again, involves using some specially scaled paper and plotting by hand. Are these two methods equivalent? Thanks for any help.
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