The negative component of y-asix indicates the kind of response, whereas the positive part indicates the type of reaction.
On a DSC curve you have the heat flux (dq/dt ; on the y axis) as a function of temperature. Thus, the vertical downward direction indicates an absorption of heat (endothermic reaction).
There is a very explanatory video on youtube.
https://www.youtube.com/watch?v=MRJXMEIpmpU
There are two types of DSC instruments: heat flex type and power compensation type. In the original data, heat flex type DSC (and DTA) usually suggests exothermic change in the positive direction. In the power compensation type DSC, the endothermic change (positive enthalpy change) is in positive direction. Therefore, the direction of exothermic and endothermic changes should always be suggested in the DSC figures.
Dear Debashish Nayak if you don't know the y-asix on your DSC, then run analysis of zinc (it's used for calibration) or caffeine (it's easy to find). If you have a peak upwards, so upstream is endo effect and vice versa. Example attached.
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