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A pop or pull operation: a data item at the current location to which the stack pointer points is read, and the stack pointer is moved by a distance corresponding to the size of that data item. There are many variations on the basic principle of stack operations. Every stack has a fixed location in memory at which it begins.
R7 is the program counter. Any register can be a stack pointer but R6 is used for hardware interrupts and traps. VAX [32] 16: The general purpose registers are used for floating-point values as well. Three of the registers have special uses: R12 (Argument Pointer), R13 (Frame Pointer), and R14 (Stack Pointer), while R15 refers to the Program ...
In 8086, the main stack register is called "stack pointer" (SP). The stack segment register (SS) is usually used to store information about the memory segment that stores the call stack of currently executed program. SP points to current stack top. By default, the stack grows downward in memory, so newer values are placed at lower memory addresses.
The stack is often used to store variables of fixed length local to the currently active functions. Programmers may further choose to explicitly use the stack to store local data of variable length. If a region of memory lies on the thread's stack, that memory is said to have been allocated on the stack, i.e. stack-based memory allocation (SBMA).
The instruction counter is at the lower left. The program counter ( PC ), [ 1 ] commonly called the instruction pointer ( IP ) in Intel x86 and Itanium microprocessors , and sometimes called the instruction address register ( IAR ), [ 2 ] [ 1 ] the instruction counter , [ 3 ] or just part of the instruction sequencer, [ 4 ] is a processor ...
Register R7 is the program counter (PC). Although any register can be used as a stack pointer, R6 is the stack pointer (SP) used for hardware interrupts and traps. R5 is often used to point to the current procedure call frame. To speed up context switching, some PDP-11 models provide dual R0-R5 register sets.
These have only an 8-bit stack pointer (in SPL), and only support the 12-bit relative jump/call instructions RJMP/RCALL. (Because the AVR program counter counts 16-bit words, not bytes, a 12-bit offset is sufficient to address 2 13 bytes of ROM.) Additional memory addressing capabilities are present as required to access available resources:
Special function registers are in the upper area of addressable memory, from address 0x80 to 0xFF. This area of memory cannot be used for data or program storage, but is instead a series of memory-mapped ports and registers. All port input and output can therefore be performed by memory move operations on specified addresses in the SFR region.