Describe the operation of a phase-change memory (PCM) device.
Phase-change memory (PCM) operates by exploiting the reversible phase change in chalcogenide materials (e.g., GST) between crystalline and amorphous states with the application of heat. This change in phase alters the material's resistance, allowing data to be stored as binary information. PCM is known for its high speed, endurance, and non-volatility.