Formal Definition
The Counter machine reference model consists of a finite set of registers r1 ... rn, each of which can hold a non-negative integer, r0 (always zero), and a finite list of instructions I1 ... Im. Each of the instructions in this list is one of the following:
INC(j)— increment the value of register rj by 1; go to the successor instruction (e.g. instruction that is numerically next-in-sequence).DEC(j)— If the contents of r is not 0 (not empty) then decrement the value of register rj by 1, else the contents of r=0; go to the successor instruction.JZ (j, z)— If the contents of register rj equals Zero then Jump to instruction Iz else go to the successor instruction.HALT— halts the computation.
Formal Semantic:
| Instruction | Effect on register | Effect on Instruction Counter (IC) |
|---|---|---|
| INC ( j ) | + 1 → j | + 1 → IC |
| DEC ( j ) | IF > 0 THEN - 1 → j ELSE 0 → j | + 1 → IC |
| JZ ( j, z ) | IF =0 THEN Iz → IC ELSE + 1 ) → IC |
Read more about this topic: Counter Machine Reference Model
Famous quotes containing the words formal and/or definition:
“Good gentlemen, look fresh and merrily.
Let not our looks put on our purposes,
But bear it as our Roman actors do,
With untired spirits and formal constancy.”
—William Shakespeare (1564–1616)
“Scientific method is the way to truth, but it affords, even in
principle, no unique definition of truth. Any so-called pragmatic
definition of truth is doomed to failure equally.”
—Willard Van Orman Quine (b. 1908)