I want to make an orchestra sound.

I used FL studio, but the legato isn't smooth enough, it immediately shifts notes and sounds awful.

Are there any programs that do what I am looking for, or does anyone know how to get FL studio to do what I want?
are the strings in FL a synth or a wav sample?

if its a synth, you can go into the channel settings and find the portamento function. turn it up just a bit, it pretty much adds a slide transition between each note.
I prefer the East West Symphonic Orchestra software for any ensemble strings I need.
I would do what allstrats says for the minute. It's very easy to do, and you can also try adjusting the attack and release to get a better sound. A longer attack will give you that smooth sound you're after.

Alternatively, there are a lot of sample sets on the market, such as Garritan Personal Orchestra, that you could use, but these are harder to get to grips with.
There is poetry in despair.
I'd go against Garritan unless you cannot afford anything better...the sounds are weak.
There are some ok sounding ones I use - you'll have to google them.

Cellofan - good natural sounding single cello sound. has quite a small range of notes though.

DSK strings - good range of sounds, probably the best all round.