open System
let main() =
   Console.Write("What''s your name? ")
   let name = Console.ReadLine()
   Console.Write("Hello, {0}n", name)
   Console.WriteLine(System.String.Format("Big Greetings from {0} and {1}", "TutorialsPoint", "Absoulte Classes"))
   Console.WriteLine(System.String.Format("|{0:yyyy-MMM-dd}|", System.DateTime.Now))
main()

When you compile and execute the program, it yields the following output −

What''s your name? Kabir
Hello, Kabir
Big Greetings from TutorialsPoint and Absoulte Classes
|2015-Jan-05|

The System.IO Namespace

The System.IO namespace contains a variety of useful classes for performing basic I/O.

It contains types or classes that allow reading and writing to files and data streams and types that provide basic file and directory support.

Classes useful for working with the file system −

• The System.IO.File class is used for creating, appending, and deleting files.
• System.IO.Directory class is used for creating, moving, and deleting directories.
• System.IO.Path class performs operations on strings, which represent file paths.
• System.IO.FileSystemWatcher class allows users to listen to a directory for changes.

Classes useful for working with the streams (sequence of bytes) −

• System.IO.StreamReader class is used to read characters from a stream.
• System.IO.StreamWriter class is used to write characters to a stream.
• System.IO.MemoryStream class creates an in-memory stream of bytes.

The following table shows all the classes provided in the namespace along with a brief description −

Example

The following example creates a file called test.txt, writes a message there, reads the text from the file and prints it on the console.

Note − The amount of code needed to do this is surprisingly less!

open System.IO // Name spaces can be opened just as modules
File.WriteAllText("test.txt", "Hello Theren Welcome to:n Tutorials Point")
let msg = File.ReadAllText("test.txt")
printfn "%s" msg

Hello There
Welcome to:
Tutorials Point