The importance of the informal information system is reflected in the fact that the informal information system is the ” twin system” of the formal information system in the management of organizational activities, whether it is in providing support for formal channels of communication or in helping the administration to deal with different situations. Any administrative activity must be accompanied by informal information using. However, the informal information system has not received sufficient attention in organizational thought compared to the attention given to the formal information system at the level of research or even management practices. The aim of this study is to demonstrate the importance of the informal information system as the “twin system” for the formal information system in the organization. To achieve this, a comparison was made between the two systems through several axes: concept, elements, importance, networks of data and information flow, characteristics and effectiveness.
JEL classification numbers: D8 , M1
Keywords: informal information system, formal information system, twin system, comparison, networks of data and information flow.