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:
“Two clergymen disputing whether ordination would be valid without the imposition of both hands, the more formal one said, “Do you think the Holy Dove could fly down with only one wing?””
—Horace Walpole (1717–1797)
“Mothers often are too easily intimidated by their children’s negative reactions...When the child cries or is unhappy, the mother reads this as meaning that she is a failure. This is why it is so important for a mother to know...that the process of growing up involves by definition things that her child is not going to like. Her job is not to create a bed of roses, but to help him learn how to pick his way through the thorns.”
—Elaine Heffner (20th century)