When the program size is larger than the RAM size how will the program get executed?

Answer 1

The simple answer is it won't execute at all. If a program cannot fit into the system's physical memory (RAM) then it cannot execute, period. The solution is to modularise the program such that the executable is small enough to remain resident while auxiliary functions are placed in more transient libraries that can be freely loaded and unloaded as and when required.

Although virtual memory can make it appear as if your system has far more memory than physically exists in the system, there are still limitations. For example, a 32-bit Windows operating system has a maximum address space of exactly 4 GB (2^32 = 4,294,967,296 bytes), but a single process can only utilise 2 GB at most -- the other 2 GB is reserved for use by the system. Thus the largest executable is limited to no more than 2 GB in size. However, the actual limit is less than 2 GB because the size of the executable on disc is (usually) much lower than its runtime size. This is because every process requires at least one fixed-length call stack (one for each thread of execution in the process) and the process' data segment can generate all zero-initialised static variables, constants and globals at loadtime (they are not stored in the executable, unlike non-zero-initialised statics are), not to mention anonymous variables that are generated on the heap at runtime.

For 64-bit systems, although the theoretical address space is 2^64 = 18,446,744,073,709,551,616 bytes (18 exabytes), that's far more memory than physically exists on the planet! With current technology it is simply not possible to design a system that can accommodate the full complement of memory, thus there has to be a more practical physical limitation. In the case of Windows 10 x64, the physical limit is 2 TB (or 128 GB in the case of Windows 10 Home edition). Even the virtual address space must be limited and this is set at 8 TB for x64 processes (or 7 TB for Intel Itanium-based systems) and 128 TB for Server editions.

Answer 2

excuted