Patent Document ID: 4504925
Application ID: 06340388

Base Claim:
1. A self-shifting last-in-first-out stack for a data processing system, comprising a linear array of data storage cells interconnected for enabling stored data to be shifted to or from an adjacent cell; and a control circuit having a linear array of control cells corresponding to the linear array of data storage cells with each (n)th control cell from the top of the stack being connected to the corresponding data storage cell and its adjacent data storage cells for sensing the storage states of the data corresponding storage cell, and its adjacent data storage cell, and its adjacent data storage cells and in response to said sensed states, for causing stored data to be shifted from the (n)th cell in the array of data storage cells from the top of the stack into the (n+1)th cell whenever the (n)th cell is full, the (n+1)th cell is empty and the (n-1)th cell is full; and for causing stored data to be shifted into the (nth) cell from the (n+1)th cell whenever the (n)th cell is empty, the (n+1)th is full and the (n-1)th cell is empty, wherein n is an integer greater than one.

---

Claim 2:
2. A stack according to claim 1, wherein within the linear array of data storage cells the output of each (n)th cell is connected to the input of the (n+1)th cell by a push gate and is connected to the input of the (n-1)th cell by a pop gate, and the input of each (n)th cell is connected to the output of (n+1)th cell by a pop gate and is connected to the output of the (n-1)th cell by a push gate; wherein each push gate is connected to the control circuit for shifting data down from the top of the stack in response to a push signal from the control circuit; and wherein each pop gate is connected to the control circuit for shifting data up toward the top of the stack in response to a pop signal from the control circuit.