Uhm, no. I suggest you read up on developing cross-platform apps. It's completely possible (albeit with some adjustments needed, usually) to develop one code, and then port that code to work with different OSes - as @sarahk said, you can build apps that compile for both systems (or more).
Point me to an article that suggests you can do that WITHOUT some cheesy method of using JavaScript/HTML5 embedded then I will gladly stand corrected.
Well, not entirely what I was thinking off, but this is one way to do it: http://oleb.net/blog/2014/05/how-dropbox-uses-cplusplus-cross-platform-development/
Not close. You told me to do my research.... I have. There isn't a reliable portable solution between iOS and android since they are two very different OS... The only cross support services aren't cross supported languages. They take HTML5 and JavaScript "apps" and embed them in to a mini browser that acts as if it's an app... And they are in 2 different languages. The only solution is to program 2 versions using similar logic. Have you programmed for a mobile device? If not...do a little further research and you will see.
Uhm - you still need to develop different front-ends to follow different practices for the different OSes, but the background processes can be coded using cross-platform SDKs, frameworks and code - as for instance C++. And no, these do NOT simply take a HTML5/CSS/JS solution and embed them. I haven't tried it, but also, Unity can provide for both OSes, although of course, this is more of a gaming environment than anything meant for pure professional app-coding. It's completely possible, but again, it involves a bit of a compromise - still better than coding separately for both OSes.