I have a multiple entry c type valid tourist visa from Switzerland. My visa has a remark tourism in it. I have used it for tourism purpose already. During my 1 travel for personal tourism purpose, I entered Prague by road travelled to Zurich and exited from Zurich. I need to travel to Spain to attend an annual event/conference for one of the system my company use. It’s mainly a gathering event to connect and discuss on the system and no work or meeting involved. Can use the same tourist visa to travel to Spain this time.
Schengen Visas have two different types, short-stay and long-stay. Your Type C visa from Switzerland is a short-stay Schengen Visa. See this page from Switzerland's Federal Department of Foreign Affairs (FDFA) for a basic overview of these visa types.
Without knowing your nationality I cannot provide you with a complete answer, however Schengen Visas are valid for all member states of the Schengen Agrea, meaning your visa should be valid for entry to Spain. Under the rules for a Type C visa, attendance of a conference is a permitted activity, given that you do not take up work. This is different from the Type D national visa where you would be taking up work on a long-stay in a member state. While I am not a legal professional and I suggest you research the topic further on your own and with the aid of a professional, there is no distinction within the Type C visa between tourism and business other than the remark left for the primary visit purpose. This leads me to believe that while it was issued for the primary purpose of tourism, engaging in another permitted activity on a short-stay in the Schengen Area, such as attending a conference, should be allowed.
I would reccomend you read up on this page from the German Missions in the United Kingdom, which provide in English, information on professional activities not classified as economic activities/work, which should provide you with some guidance on what you are allowed to do on a Type C visa. It may also be beneficial to try contacting the embassy/consulate that issued the visa for any questions.