The MSI character set consist of the numbers 0..9 as well as two "guard" characters (representing the beginning and end of the barcode).

So, like Interleaved 2-of-5 and UPC, MSI is an all-numeric language, not support alphabetic characters.

The bit representation is same with Plessey:

But the digit representation is more simple:

Each digit number is represented by four bit.

Except the start and stop bits, If you only calculate the bar (horizontal black line), the wide bar means ‘1’ and the narrow bar means ‘0’,

then it is the same rule as using binary to represent the digit:

Digit 0 = 0000b

Digit 1 = 0001b

Digit 2 = 0010b

Digit 3 = 0011b

...