What is the SELECT key?

Question

While searching for some shortcuts for my application, I stumbled over some constants in the C# Keys enumeration:

• Select
• Separator
• ProcessKey
• Pa1
• Crsel
• Execute

There's no further information for them on MSDN.
The questions is: which keyboard key corresponds to those values?
(And are they on a standard keyboard layout?)

Answer 1

Keys like Select, Attn, Pa1, etc. that can be found from Microsoft documentation for virtual key codes, are remnants from the early PC era when terminal emulation was still a dominant field of application. For example the LK201 keyboard used in DEC VT220 terminal and Rainbow 100 computer has a Select key.

Most prominently however these keys appear on a 122-key IBM Model F keyboard for 3270/3179/3180/5250 terminals:

(image source: ClickyKeyboards.com)

IBM included support for multiple keyboard types in the original Model 5150 PC specification. Even though the first PC keyboard was the 83-key Model F, other keyboards can be used with an adapter board. In fact, IBM marketed a 3270 PC which was a set of expansion boards in a PC XT, making it a fully fledged 3270 terminal.

Further reading:

• https://deskthority.net/wiki/IBM_Model_F
• https://www.rs-online.com/designspark/a-fresh-look-at-ibm-3270-information-display-system

Answer 2

VK_SELECT is the key code for a Select key that doesn't exist on most keyboards. I'm pretty sure that I haven't seen one.

You can check to see if your keyboard supports it by calling the MapVirtualKey function, which can map the virtual key code to a keyboard scan code. If the function returns 0, then there is no mapping.

I created a little Windows Forms app that illustrates this. Just make a form and hook up a KeyDown handler:

using System;
using System.Runtime.InteropServices;
using System.Windows.Forms;

namespace testoForm
{
    public partial class Form1 : Form
    {
        [DllImport("user32")]
        static extern UInt32 MapVirtualKey(UInt32 nCode, UInt32 uMapType);
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_KeyDown(object sender, KeyEventArgs e)
        {
            ShowKey(e.KeyCode);
        }

        private void ShowKey(Keys key)
        {
            var keyCode = (UInt32)key;
            var scanCode = MapVirtualKey(keyCode, 0);
            var s = String.Format("VK = {0:X2}, SC={1:X2}", keyCode, scanCode);
            MessageBox.Show(s);
        }

        private void button1_Click(object sender, EventArgs e)
        {
            ShowKey(Keys.Select);
        }
    }
}

If you press a key, a message box will show the key code and the mapped scan code. I added a button that will show the scan code for the Select key. On my system, the function returns 0 for Keys.Select.