What detects presence or absence of marks in a predetermined place in a computer?

In a computer, the presence or absence of marks in a predetermined place is typically detected by a combination of hardware and software components. For example, memory management systems, such as those used in RAM or storage devices, utilize control circuits to read and write data at specific addresses. Additionally, software algorithms can query these addresses to check for specific values or markers, facilitating tasks like error detection and data integrity verification.