Covering technology
For a process, it is not necessary to load all the instructions and data of the program into memory and then execute it from the beginning . The program is divided into several functionally independent program segments. According to the logic structure of the program, the program segments that do not need to be executed at the same time share the same memory area . When the first program segment of the relevant program segment has been executed, the subsequent program segments Transferring from external memory to memory to cover the previous program segment divides the program into several functionally independent program modules according to its own logical structure. Those modules that will not be executed at the same time share a memory area and run in chronological order. The covering technology must be the mutual covering of several independent program segments in the same process, that is, these independent program segments have no mutual calling relationship and have nothing to do with each other . Therefore, the programmer must give a logical coverage structure between the various modules in the program, which makes the programmer more burdensome.
Exchange technology
To process units.
The operating system saves the content of the entire address space of a process to the external memory (swap out) , and reads the address space of a process in the external memory into the memory (swaps in), and the size of the swap in and out content is The address space of the entire program.
Virtual storage technology
The process is divided into sections or pages to segment or page units.
The virtual storage is a page or paragraph as a unit, the process is divided into sections or pages of memory for differentiation, if the process required more memory than the system memory, the process can also be run as part of the process may change to the external memory on .