A basic Dart program

The following code uses many of Dart’s most basic features:

printInteger(int aNumber) // Define a function. 
{ 
   print('The number is $aNumber.'); // Print to console. 
}

// This is where the app starts executing. 
main() 
{
   var number = 42; // Declare and initialize a variable. 
   printInteger(number); // Call a function.
}

Here’s what this program uses that applies to all (or almost all) Dart apps:

• // This is a comment (A single-line comment. Dart also supports multi-line and document comments. For details, see Comments)
• int A type (Some of the other built-in types are String, List, and bool) 
• 42 (A number literal. Number literals are a kind of compile-time constant)
• print() (A handy way to display output)
• '...' (or "...") (A string literal)
• $variableName (or ${expression}) (String interpolation: including a variable or expression’s string equivalent inside of a string literal. For more information, see Strings) 
• main() (The special, required, top-level function where app execution starts. For more information, see The main() function) 
• var A (Way to declare a variable without specifying its type)