Models of computation

Arithmetic model

• Variables can hold any integer
• Each variable takes 1 unit of space
• Operations are +, -, *, /
• Each operation takes 1 unit of time
• Assignments, I/O, branching, comparisons take no time

Bitwise model

• Variables can have values 0 or 1
• Each variable takes 1 unit of space
• Operations are and, or, exclusive-or, not
• Each operation takes 1 unit of time
• Assignments, I/O, branching, comparisons take no time

Comparison model

• Variables can hold any integer
• Any mathematical operation can be done in no time
• Assignments, I/O, branching take no time
• Comparisons take 1 unit of time