1) user inputs (paste or load as .txt file) lines of text into one window.
2) user then inputs (paste or load as .txt file) lines of other text into a second window.
3) The program looks up the strings (line by line) from the 2nd window in the first window and copies all UNIQUE versions from window 1 to a 3rd output window where the user can then CTRL-A/CTRL-C copy it to the clipboard or save it as a .txt file.
There is a tiny bit of text-processing involved:
a) The lines in window 1 are all lower-case and have spaces between the words, whereas
b) the lines of text in window 2 are all upper-case (so need to call Lower()) and they have all spaces removed, so when looking up the text internally, the spaces have to be removed from the text in window 1.
c) Finally, the lines in window 2 consist of 2 parts which are separated by a unique character, so when looking up the text, you only look up the first part of each line up to the unique character.
line 1: here is some text
line 2: and some other text
line 3: and text with a few numbers
line 1: ANDSOMEOTHERTEXT-THISISAFTERTHESPECIALCHARACTER
line 2: ANDTEXTWITHAFEWNUMBERS-SOMESTUFFWEIGNORE
line 3: ANDTEXTWITHAFEWNUMBERS-SOMEOTHERSTUFFWEIGNORE
in this example, line 2 and 3 are identical up to the special character, so the output is
line 1: and some other text
line 2: and text with a few numbers
in terms of speed and memory requirements, the user can copy up to around 500 lines of text into each window, each up to roughly 40 characters long (but it should not be fixed at 40 chars, or 500 lines, this is just to give you an indication of what can happen in practice).