Kotev

כותב is doing an action that will form permanent words, numbers or pictures. That action does not necessarily need to be a form of writing. Instead, any action that will form words will be an איסור מדאורייתא.

מוחק is the reverse of כותב. That is, the removal of letters in order to make space for new letters to be written down.

The words that constitute a biblical prohibition are specifically כתב אשורי (see אור זרוע brought down by the רמ”א and יביע אומר defending the position against the מש”ב). Therefore, any words written in contemporary times are only rabbinic in nature. This is the biggest חידוש in regards to הלכות כותב and should only be relied on when no other היתירים are applicable.

While doing action with left hand is usually not considered a שינוי for הלכות שבת, by כותב since the resultant product is inherently subpar quality the writing is not considered כתיבה for דאורייתא. Nonetheless, using left hand to stamp writing would not be considered a שינוי because the finished result is similar in quality.

The writing must last for at least a couple of days. Writing that does not have a permanent feature will not be אסור מדאורייתא.

Triggering writing to appear is also considered a איסור מדאורייתא. Therefore, walking in front of an actively recording digital camera could be considered biblically prohibited, if the image is displayed on a monitor and the one recorded has a status of איכפת ליה. Therefore, imaging modalities are אסור מדאורייתא if they are not viewed digitally. If they are viewed digitally and not stored on film they should only be אסור מדרבנן (see below). However, EKG monitors that are only רושם would be אסור מדרבנן.

For electrical writing, writing on a touchscreen is better than writing on a physical keyboard (for electricity issue purposes, see that section in בונה). In general, writing on a computer is not considered writing at all מדאורייתא. Therefore for a חולה שאין בו סכנה, typing with a שינוי would offer a שבות דשבות. (However, writing in כתב לועזי (that is not מדאורייתא) will not be a קולא because typing is not considered כתיבה at all according to this position. If you accept the alternative view that typing is כתיבה then כתב לועזי would be a היתר but typing with a שינוי would not be as the resultant product is the same).

Printing is an איסור דאורייתא of כתיבה because the result is actual כתיבה. (While it should not matter if the printing was done by שינוי because the resultant product is the same, Rav Neurbit seems to think that it would be better to do it בשינוי for חולה שיש בו סכנה). Obviously, the best solution would be to ask a גוי and then it would only be a דרבנן. Adding, the דרבנן of כתב לועזי, you would have שבות דשבות. However, if the printer is on a timer there may only be a גרמא issue and it once again would only be a דרבנן.

It seems that people accept that its better to be lenient if you are pulling up information already stored on the computer verse typing new information into the computer. This has nothing to do with מלאכת כותב. Rather, there may be an איסור דאורייתא of בונה when you store new information in a computer. This too, was addressed in מלאכת בונה.

Opening packages while ripping the letters would only be an איסור מדרבנן as you are not intending to write something in its place. It is then best to open packages in between the letters. If not, there is yet another מדרבנן to rely on as you are not actually erasing the letter because you can always put them the two sides back together again and reform the letter.