Understanding computer memory is fundamental to comprehending how digital systems function. Memory types are broadly classified based on whether they retain data when power is removed. This characteristic is known as volatility.

Memory Volatility Explained

Memory volatility refers to the ability of a memory device to retain stored information without power. There are two main types:

• Volatile Memory: This type of memory requires power to maintain the stored information. If the power is turned off, the data is lost. Think of it as a temporary workspace for the CPU.
• Non-Volatile Memory: This type of memory can retain stored information even when power is removed. It is used for permanent storage of data and instructions that need to persist.

ROM: Non-Volatile Memory

ROM stands for Read-Only Memory. As its name suggests, data stored in ROM is typically written once (during manufacturing or programming) and then can be read multiple times. The crucial characteristic of ROM is that it is a non-volatile memory. This means that the data stored in ROM remains intact even when the computer or device is turned off and power is no longer supplied.

ROM is commonly used to store firmware (e.g., BIOS in computers), boot-up instructions, and other essential programs that do not need to be changed frequently and must be present when the system starts.

RAM: Volatile Memory

RAM stands for Random Access Memory. Unlike ROM, RAM is a volatile memory. This means that RAM requires a constant power supply to maintain the information stored in it. As soon as the power is switched off, all the data stored in RAM is lost. RAM is used as the primary working memory for the CPU because it allows for very fast reading and writing of data. When you open a program or file, it gets loaded into RAM for the CPU to access quickly.

PLA and PLD: Logic Devices, Not Primary Memory

Options such as PLA (Programmable Logic Array) and PLD (Programmable Logic Device) are types of digital integrated circuits used to implement custom logic functions. While some PLDs might contain small amounts of memory elements (like flip-flops or lookup tables in FPGAs, a type of PLD), their primary function is logic implementation rather than general-purpose data storage like RAM or ROM. They are not typically categorized as "non-volatile memory" in the same context as ROM for storing persistent data or programs.

• PLA (Programmable Logic Array): A type of PLD that uses programmable AND gate array and programmable OR gate array to implement sum-of-products logic expressions.
• PLD (Programmable Logic Device): A generic term for integrated circuits that can be configured by the user to implement digital logic functions. This category includes PLAs, PALs (Programmable Array Logic), CPLDs (Complex PLDs), and FPGAs (Field-Programmable Gate Arrays).

Therefore, based on the definition of non-volatile memory, ROM is the correct answer as it retains data without power.