Include the SML# installation directory in your command load path, so that you can run SML# by the name smlsharp. When invoked without any parameter, SML# stars its interactive session by printing the following message and waits for your input.

$ smlsharp
SML# version 3.7.1 (2021-03-15) for x86_64-pc-linux-gnu with LLVM 11.0.0
#

The “# ” character is the prompt SML# prints. In this document, we write “$ ” for the shell prompt.

After this message, the compiler repeats the following steps.

1. 1.

   Read the user input up to “;”.

2. 2.

   Compile the input program and execute it.

3. 3.

   Print the result.

The following is a simple example.

# "Hello world";
val it = "Hello world" : string

The first line is the user input. The second line is the response of SML# system. As seen in this example, the compiler prints the result value with its type, and binds it to a name for subsequent use. If the user does not specify the name, the compiler uses “it” as the default name.