The simplest computational resources are computation time, the number of steps necessary to solve a problem, and memory space, the amount of storage needed while solving the problem, but many more complicated resources have been defined.
Examples of problems might be "given an integer n, determine whether n is prime", or "given two numbers x and y, calculate the product x*y".
As the inputs get bigger, the amount of computational resources needed to solve a problem will increase.
Resource usage is often partially quantified using Big O notation.
A bounded Turing machine has been used to model specific computations using the number of state transitions and alphabet size to quantify the computational effort required to solve a particular problem.