Which unit in a computer generally contains volatile information?

The memory unit is responsible for storing data that can be quickly accessed and manipulated by the CPU. This type of memory, often referred to as RAM (Random Access Memory), is volatile, meaning that it loses its stored information when the power is turned off. This characteristic makes it essential for running applications and processing data on-the-fly while the computer is operational.

In contrast, other units mentioned, such as the secondary storage unit, are designed for long-term data retention and do not lose information when the power is off, making them non-volatile. The arithmetic and logic unit (ALU) performs calculations and logical operations but does not store data in a manner that is considered volatile or non-volatile in terms of information retention. The input unit primarily facilitates data entry into the computer system and does not store data at all.

Thus, the memory unit is the only component that is fundamentally defined by its volatility in relation to the other options.