Management is a process of organizing work activities based on four functions which are planning, organizing, leading and controlling. This definition shows management as a continual activity, involving goal achievement, and knowing how to carry out management's major functions (Bartol & Tein 2007).
An organization needs managers to manage its functions. Manager is the kind of people who has responsibility to implements the management process (Davidson et al. 2009, p10). According to Robbins et al. (2006, p10), in the early twentieth century a French company suggested that all managers bear responsibility for five functions which are planning, organizing, leading, controlling and commanding. Nevertheless in the modern century, the functions decreasing into four basic and most important functions, like saying in the first paragraph. As described by Davidson et al. (2009, p5), planning means managers need to forecast the situation of the organization in the future, set up goals and make plans to realize the goals; moreover, managers are responsible for arranging human and recourses so that plans could be successfully achieved, this function is called organizing; for leading, that is managers have to encourage people in the organization and lead them to engage in the work behaviors to reach organizational goals; the last function that managers perform is controlling which means the manager should ensure that people are carrying on the right tasks and rectify as soon as possible when the work running to