Memory Management in Operating System #:1 Compile Time, Load Time and Run Time Binding

Описание: Memory management is one of the most important jobs of operating system. Memory management means how to share, protect, re-locate, allocate and de-allocate computer memory in multi-programming systems.
Address binding means the procedures and techniques deployed to move a program from secondary storage to primary memory and allocate space to it.
Compile Time Binding: At the time of compilation, it is known that where a process will reside in main memory. The address binding or address mapping is done at the time of compilation. Physical address is equal to the logical address. If the space reserved for the process is occupied by some other process, then the code must be re-compiled.
Load Time Binding: In this address binding technique, the addresses generated by the linker are local addresses irrespective of physical memory consideration, then the loader adds some value with every of its addresses and generate physical address. The value that is added by the loader with every address of the compiled program is stored in Memory Relocation Register. If, by some way, the location referenced by the Memory Relocation Register is occupied by OS then the program needs to be reloaded, by reloading the value of Memory Relocation Register is changed and hence the entire program is shifted to some new location.
Run Time Binding: The exe file generated by the loader still has relative addresses and does not have the actual physical address. The decision of storing a program at a location is defined by the CPU itself at run time. Every now and then the process is moved place to place in the Primary Memory. This run-time binding is performed by page table or segment table and will be discussed latter on. These address binding mechanisms are very crucial for memory management, they are also called address mapping.