What Is a Memory Map?

Although it might seem like it, the memory on a computer is not like a gigantic bin into which data can be dumped. Instead of a bin, computer memory is more like a filing cabinet. The arrangement of the files on a computer's memory is preserved in a virtual file known as the memory map. The memory map contains information about each "drawer" of the computer's memory. During operations, the operating system uses the memory map to learn how to access and utilize the amount of available memory on the computer system.

The memory map contains a full readout of each available slot in system memory. A simple way to visualize this is as a grid layout. Each file in the computer's memory has a specific address, coordinates that indicate its location. For each memory coordinate or address on the map, the memory map lists whether the memory is available or whether some other program has reserved it for future use. This keeps all memory information on the computer distinct and separate for each program, preventing memory errors and other problems.

Without a working map, the integrity of the information stored in memory would be in constant jeopardy. Imagine that a financial program and a video game were running simultaneously on a single computer. The financial program stores a bank account balance in address one in memory. Without a memory map to guide the process, that information could easily be overwritten by the video game program when it stores a high score. Now, instead of a balanced bank account, the computer is adjusting financial data based on video game performance. Even worse, without a memory map to point out the difference, the system will have a greatly-reduced chance of catching the error.

The functionality of a map depends on the way it is used. During the computer's start-up process, the map informs the operating system of the total amount of memory on the system, and makes the memory map available to the operating system, providing a basic layout. Memory maps are also critical to virtual memory and debugging programs, though. In virtual memory, the map provides an overlay between the virtual memory and the actual physical addresses, as a translator might convert a map from miles to kilometers. In debugging, the map is used to check memory addresses against stored data, ensuring that everything is in its proper place.