### 23.4 Querying memory available resources ¶

The amount of memory available in the system and the way it is organized determines oftentimes the way programs can and have to work. For functions like `mmap` it is necessary to know about the size of individual memory pages and knowing how much memory is available enables a program to select appropriate sizes for, say, caches. Before we get into these details a few words about memory subsystems in traditional Unix systems will be given.