The table tells you the (Scan) Codes to expect to see if you interface a PC(AT) Keyboard to a circuit.

The First column of the table represents the Keyboard Key you Pressed (it may have multiple functions such as the 1 key which also serves as the ! key).

The Second and Third columns is the Scan Code in either Decimal or Hex.

The remaining columns are native translations to ASCII, or with the SHIFT Button depressed, or with the CTRL Button depressed or with the ALT Button depressed.

Some keys generate TWO characters. On some Keyboards the first character is a Hex 00, on others it's a Hex E0. This indicates there is a second character following.

Unfortunately, whoever at IBM thought of this system must have been seriously pissed one day because if you press the PAUSE/BREAK key you get Hex E1 14 77 E1 F0 14 F0 77.