In cybersecurity, PCR stands for Platform Configuration Register. PCRs are special registers within a Trusted Platform Module (TPM) that store cryptographic hashes representing the state of a computer system's hardware and software components during the boot process. These values are used to ensure system integrity by verifying that the system has not been tampered with. When a device boots, measurements of firmware, bootloaders, and operating system components are taken and stored in PCRs. Security applications can later check these values to confirm that the system remains in a trusted state, enabling secure operations such as disk encryption and remote attestation.