Storage organization

The runtime storage might be subdivided into
- Target code
- Data objects
- Stack to keep track of procedure activation
- Heap to keep all other information

This kind of organization of run-time storage is used for languages such as Fortran, Pascal and C. The size of the generated target code, as well as that of some of the data objects, is known at compile time. Thus, these can be stored in statically determined areas in the memory. Pascal and C use the stack for procedure activations. Whenever a procedure is called, execution of an activation gets interrupted, and information about the machine state (like register values) is stored on the stack. When the called procedure returns, the interrupted activation can be restarted after restoring the saved machine state. The heap may be used to store dynamically allocated data objects, and also other stuff such as activation information (in the case of languages where an activation tree cannot be used to represent lifetimes). Both the stack and the heap change in size during program execution, so they cannot be allocated a fixed amount of space. Generally they start from opposite ends of the memory and can grow as required, towards each other, until the space available has filled up.