Expressions are not allowed at the top level

You can't have executable code at the top level, as it's not clear when that code is executed.

Remove those lines, or move them into a function that can be called.

func printRange() {
    let range01INT1 = 100000 ... 199999
    print("Range:",range01INT1,"Number of numbers", range01INT1.count)
}

Hi, HulaBalooFl –

The other code in your sample indicates you've set up a new project using SwiftUI, which is a modern app centred around a graphical user interface. In that situation, the system looks for an entry point which is a struct conforming to App adorned with @main with the intent of setting up the app's interface, and then calls code within those types at appropriate times. In other words, it doesn't really run the lines of a program "top to bottom" like a traditional coder might expect.

If you're just trying to get to know the Swift language and run a sequence of lines in order with a printable output, you might want to start by choosing "New > Playground" and picking the "Blank" template, which just lets you edit and run code without building an app at all. Or perhaps, choose "New > Project" and then pick the "Command Line Tool" template, which lets you build an app without a graphical interface.

An easy solution is to put this code in onAppear:

struct ContentView: View {
 
    var body: some View {
        VStack {
            Image(systemName: "globe")
                .imageScale(.large)
                .foregroundStyle(.tint)
            Text("Hello, world!")
        }
        .padding()
        .onAppear() {
            let range01INT1 = 100000 ... 199999
            print("Range:",range01INT1,"Number of numbers", range01INT1.count)
        }
    }
}
 
 

And get:

Range: 100000...199999 Number of numbers 100000

Note it's Xcode, not CodeX