We will become very familiar with these instructions as we learn to implement them and to write simple assembler programs using them.

In the above notation, xxxxxxxxxxxx is a 12-bit binary number. Since it is a memory address, it is unsigned.

kkkkkkkkkkkk is also a 12-bit binary number, also unsigned. It is just a binary number, from 0 to 4095, and is not necessarily a memory address. The letter k was chosen because this number is a constant (konstant in German) that is plunked into the A register by the LDI instruction.