What does "runtime" mean?

This morning I was going through the Elm docs and I came across this line that caused me to pause:

In Elm, commands (Cmd) are how we tell the runtime to execute things that involve side effects.

I understood "runtime" to be the length of time a program took to run, so this sentence confused me. After talking about it with some people from RC, we learned that, depending on the context, "runtime" can mean different things:

"the runtime"/"the runtime environment" = the programming language's own internal code that runs alongside the code you provided, the environment inside of which your program runs
"at runtime" = things that don't happen until your code is running, like the way JS and Python don't always show you syntax errors until you get into the bad function
"runtime" = amount of execution time taken
"runtime" (adjective) = specifies something that happens while your code is running in the browser, eg "runtime exception"

Thanks to Juliano Solanho and Chris Ball for their help!

27 Sep 2016

What does "runtime" mean?

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