entries denoting containing scopes are obtained from the appropriate prefix of the caller's display. An inner routine which recurses creates separate call frames for each invocation. In this case, all of the inner routine's static links point to the same outer routine context. Other return state Beside the return address, in some environments there may be other machine or software states that need to be restored when a subroutine returns. This might include things like privilege level, exception-handling information, arithmetic modes, and so on. If needed, this may be stored in the call stack just as the return address is. The typical call stack is used for the return address, locals, and parameters (known as a call frame). In some environments there may be more or fewer functions assigned to the call stack. In the Forth programming language, for example, ordinarily only the return address, counted loop parameters and indexes, and possibly local variables are stored on the call stack (which in that environment is named the return stack), although any data can be temporarily placed there using special return-stack handling code so long as the needs of calls and returns are respected; parameters are ordinarily stored on a separate data stack or parameter stack, typically called the stack in Forth terminology even though there is a call stack since it is usually accessed more explicitly. Some Forths also have a third stack for floating-point parameters. Structure A call stack is composed of stack frames (also called activation records or activation frames). These are machine dependent and ABI-dependent data structures containing subroutine state information. Each stack frame corresponds to a call to a subroutine which has not yet terminated with a return. For example, if a subroutine named DrawLine is currently running, having been called by a subroutine DrawSquare, the top part of the call stack might be laid out like in the adjacent picture. A diagram like this can be drawn in either direction as long as the placement of the top, and so direction of stack growth, is understood. Furthermore, independently of this, architectures differ as to whether call stacks grow towards higher addresses or towards lower addresses. The logic of the diagram is independent of the addressing choice. The stack frame at the top of the stack is for the currently executing routine, which can access information within its frame (such as parameters or local variables) in