  The SDHCAL technological prototype is a $1 \times 1 \times 1.3$~m$^3$
high-granularity Semi-Digital Hadronic CALorimeter using Glass Resistive Plate
Chambers as sensitive medium. It is one of the two HCAL options considered by
the ILD Collaboration to be proposed for the detector of the future
International Linear Collider project. The prototype is made of up to 50 GRPC
detectors of 1~m$^2$ size and 3~mm thickness each with an embedded semi-digital
electronics readout that is autotriggering and power-pulsed. The GRPC readout
is finely segmented into pads of 1~cm$^2$. This proceeding describes the
prototype, its operation and its performance in energy reconstruction. Aspects
of the GRPC readout modelling and comparisons with simulations are also
presented.
