Whilst there are some cinemas that still retain use of 35mm projectors, it's fair to say that these are only used for special events. Modern cinema, by which I mean the industry that distributes and exhibits mainstream content (so any new releases), are exclusively distributed in digital format.
In early 2002, Hollywood sought to standardize this technology for the incredible advantages it possessed. Digital projectors have been industry standard since 2005 in the UK, but much earlier in America and China. Due to its cinematic heritage and relative size, the UK is almost always used as the 'control' in rolling out cinematic technologies. It is usually measured as an experiment, and just as the introduction of sound, colour and 3D cinemas required refits and refurbishment, this is now happening with digital distribution.
The rest of the world is moving in exactly the same direction, but with different levels of immersion in the cinematic process.
Many cinemas use a system called DCP which is literally a USB pen that gets shipped around inside a case. It improves accountability on behalf of cinema-pirates, as each Pen has a certain number of licences on it. A slightly more old fashioned variation of this is large portable hard-drives, but these are being phased out of circulation too.
A DCP is simply a file that requires activation from a licence. The DCP is signed for by the cinema, and then the projectionist is given the licence activation code to allow the content to be played. Some cinemas have a licence retainer, or master licence for content.
Because most multiplex cinemas are part of an exhibition chain, they are typically less vigilant in safeguarding their content, and will handle the management of their content internally, negating such stringent protection.
Increasingly, satellite technology is being explored in order to reduce the cost of distribution (which has already more than halved in the past 10 years). Under satellite systems, the film is literally downloaded from a secure server and the film is activated for use via satellite; projectors can even be controlled remotely through the satellite, which centralizes the entire process externally.
This is a method that has been spearheaded in the UK by such projects as National Theatre Live and Opera Live. Whilst they do broadcast globally, they remain a minority interest for exhibitors (although a growing one, due to their success). The legacy of these projects will not, however, come from their content but by their method of distribution. Even now, many distributors are promoting their ease of use as leverage to persuade developers to pursue satellite distribution as it reduces the overheads dramatically.
As with many instances of private enterprise, the real driving force behind satellite distribution is the revenue stream it creates, and the relative immediacy of this income.
It's the worst kept secret of most cinemas that the most lucrative single-income source is the adverts that are exhibited before a feature.
To explain: a single multiplex may have an opening weekend for a particular film that takes a significant box office. To take this quarters tentpole (Avengers:Age of Ultron) as an example;
A 12 screen MP may take an optimistic BO:W/E of £36k (approx $55)... so if a film has legs for a month and its returns are inevitably diminishing week by week, we're looking at a best case scenario of £70k ($100,000 dollars): and let me stress this would be an absolute wet dream for a cinema to make these numbers on a single film. Advertisement, by comparison? for a modest 5 screen art house cinema, you're looking at an annual income of about £200K ($300K)... and that is, most importantly, guaranteed.
Adverts don't need to be good; infact, they're often awful. They don't rely on word of mouth, critical acclaim or any amount of audience reception. They're a guaranteed revenue stream that will double the best possible B/O of any film, they're value increases proportionately to box office takings: they (sadly) represent the backbone of modern cinema.
Here's the hook: almost every advertisement content company in the world is moving not only in the direction of digital content, but they're universally moving towards satellite. Why? because, comparitively, it costs pittance.
With the exception of implementation (which usually consists of a satellite receiver and something called a LANSAT processor [Loca-Area-Network-SATellite]), this type of distribution entirely cuts out the cost of getting the content to cinemas. Distributers simply author a file, fire it out over their satellite connection for their respective exhibitors to download (or stream if its live content: hence satellite and not unpredictable fibre/internet connections) and deal with any potential problems through modifying the coding; which is in itself rare.
If we compare this to traditional methods of P&P (Print and postage), the gains are obvious.
Film has to be printed onto celluloid, which is costly and creates only one copy. If you want to open in every cinema in the US (unlikely, but lets pretend this example is a Star Wars Scenario) you're looking at 40,000 prints. Now try and imagine a global box office...so quadruple it, at least.
You also have to factor in the cost of transportation of said prints, degradations and recirculation, repair (the days of 35mm splice jobs are long gone, and not soon missed) and, most overlooked of all...insurance.
Many people realise that films stock used to be made of the incredibly flammable silver nitrate, as demonstrated during the finale of Tarrantino's Inglorious Basterds. During these early days of cinema, the relative hazard of transporting these prints was absorbed by the distribution companies.
When insurance firms became common practice, this cost was phased onto them... and when the film stock changed and became less hazardous, what did the insurance firms do.....?
Not give a f%!k.
Even up until digital content distribution, insurance companies refused to acknowledge that the relative risk of transportation had diminished, and were able to charge disproportionate costs for film distribution; a practice that continues with 35mm, although it's a dying market so prices are dropping significantly.
Satellite distribution has removed all these overheads completely, and there is simply no feasible alternative on any medium to large scale operation.
It's fair to say that most if not all cinemas are now fitted with digital projectors, and within the next 20 years (as they become satellite compatible) we will probably see the extinction of the projectionist: they'll become something that's wheeled out on special occasions to demonstrate a vestigial technology, to show off its novelty. That's more or less the case now, actually.