The paper concerns the analysis of the role of artefacts and instruments in approaching calculus by graphic-symbolic calculator at high school level. We focus on an element of the introduction of calculus: the global/local game. We discus the hypothesis that the zoom-controls of calculator support the production of gestures and metaphors that foster the shift from a global to a local point of view. The analysis of protocols confirms that the exploration of several functions through the zooming process was supported by gestures and language. They appeared during the zooming process and in pupils' answers to the tests when the calculator was no more available and when the task concerned mathematical objects. (Contains 2 figures.) [For complete proceedings, see ED489538.]