Assuming you mean having it on all the time as well, it still should not make the room "noticably" hotter. There's a little fan in the computer that keeps it from getting hot. So unless something is wrong with your computer, the answer is no.

I guess that by "it" you mean the room, not the computer. Having a computer running in your room will make it hotter, depending on the size of the room, depending on the computer and depending on how long you run it even noticeably so. The fan inside the computer will cool the computer itself, but it will increase the temperature in the room even more, since in addition to a running computer, you now have a running fan which is producing additional heat of its own. Most computers run cool enough that you won't notice a difference, but larger/faster/older computers may run hot enough for you to notice an increase in heat, especially in smaller rooms.

It depends on a number of factors; the size of the room, what's in the room, how well-insulated the room is, whether it faces the sun in the morning/daytime/evening, and as importantly, how powerful the computer is and how many peripherals you have! For example, your bog standard computer will be a pretty regular machine with mid-spec components, probably one hard drive, and an average cooling setup inside. It will probably never be 'driven' performance-wise too hard, so it'll never get too hot doing loads of processing. However, even a small PC in a smaller room will generate a fair amount of heat output - and if it's placed in an area where there's little or no circulation of colder air (or an inefficient airflow) then the heat will build up and build up. I have my PC on 24/7 in my bedroom, it's not the biggest of rooms and there's lots of clutter - and generally hardly enough space to swing a cat anyway. If I shut my window, and it's one of those warmer days, then my room can heat up quite a fair bit - it'll be anything approaching several degrees warmer than the rest of the house, sometimes as much as 7 or 8 celsius... You can feel it when you walk out of my room and onto the landing and back again. That said, my computer isn't quite 'stock'... It has a top-spec graphics card (with pro cooler fitted), an overclocked processor - which generates more heat than a standard-speed processor - and LOTS of other pieces of hardware and peripherals... All of these generate extra heat. I also have a lot more fans, which whilst moving the air through and out of my PC case more efficiently, generate their own bit of heat too... ... And that's why my bedroom window is never shut. :) This is also why some people spend a LOT (and I mean a lot, a small fortune for me) buying kit like Vapochill cases for computers, which are totally sealed and have their own built-in refrigeration unit to keep the inside of the case at MINUS degrees celsius (yes, it's true!) - but these people often also fall into the "hardcore overclocker" spectrum of PC users. There are also other ways to dissipate the heat generated bya a computer, including silent methods such as water cooling (the only noise generated is by the single fan cooling down the warmer water before it's pumped back round the system again, but a company called Zalman have just introduced a very cleverly-designed tower system for dissipating the heat in the water, so not even a single fan is involved), or for the more extreme user, things like liquid nitrogen cooling... But that's a bit too specialist, and pricey, for me.

A normal computer with an LCD monitor, without a fancy graphics card uses about 140 watts. Using a CRT monitor increases that to about 240 watts. Running a CPU-intensive screensaver all the time increases it to about 280 watts. Using a laptop computer instead of a desktop is about 40 watts instead of 140. A normal 140 watt computer makes some heat that you can feel where the exhaust fan comes out, about the same as 2 old-fashioned light bulbs do. It is enough to make a small room a little warmer, but switching light bulbs for fluorescent ones is enough to balance the extra heat. A computer with CRT, screensaver, and fancy graphics card is worse, and can add noticeable heat to a room. Another factor is cost. A computer with CRT can be 200 watts more than a laptop. At a cost in many states of $2 a year per watt, this would be $400 more if you leave both on all the time.

my comp uses 400 watts and my room is noticeably hotter. Keep in mind that it does not matter the kind of cooling you have as far as room temp goes, the only thing that matters is how many watts your comp uses (and thus disapates). ITs toasty in here...

My personal experience says YES

2-25-2017 I live in a warm climate and my computer keeps the small room comfortable for most of the day. I do have to run another heater at night.