I signed like Kristina B. I don't know why three different sign "computer". It is like the accent I guess.
In part because, just like in English, there are some times different "origins" for a concept/English gloss etc.
For example with computer. Now it refers to a desktop or laptop system. However from the first invention of the English word(and associated sign) the word "computer" changed to refer to a number of different things such as:
1)
Original meaning
A person able to do complicated mathematical calculations in their head (and sometimes with the help of a slide rule)
2)
Second generation meaning
A machine that "read" cards that were punched with a special pattern of holes - these cards carried information (sort of like really basic mini computer discs)... the card reader was called a "computer" because is computed things.
3)
Third generation meaning
A typewriter like device that had a cassette like device that stored settings etc
4)
Current meaning
An electronic device with a hard drive (either magnetic or optical) for storing programs and various files. It also contains a number of hardware components that allow the basic computer "shell" to have additional interface and display features ... this includes a CD/DVD drive, additional harddrives, screen, qwerty keyboard, mouse/trackpad, speakers etc. Current computers come in three main types: desktop, laptop/netbook and tablet.
Because the meaning of computer has gone through transition, the original sign for computer (which in many places was a "C on forehead" or similar concept indicating it was a skill in a person's brain) then transformed as "computers" went from being people, to being a machine that read cards, then to something that you sit at and interface via a keyboard ... it only makes sense that because the meaning has changed so dramatically that the signs would have changes as well. However, as with all languages, the old term isn't (quickly) completely forgotten and some people will prefer a certain sign (or English word) even if its "less popular" or "out of fashion" etc ( English examples would be ""whom","thus","thee","shan't" etc ... they are all perfectly acceptable English words, however they are considered "old fashion" and have been replaced with more modern words ... just as signs are sometimes replaced with more modern/regionally consistent signs.
I hope that helps a bit