In this system, we have a single operation— MOV, which moves the contents of one address to another address. These addresses are all absolute and are 16 bits wide, just like their contents.
There is a memory-mapped program counter, which is how control flow is handled.
start:
MOV PC, #start
Here the start:
represents a label for that region, and #start
represents the address of some spot of memory allocated to hold the constant address represented by start.