Research and Advances

An efficient machine-independent procedure for garbage collection in various list structures

A method for returning registers to the free list is an essential part of any list processing system. In this paper, past solutions of the recovery problem are reviewed and compared. A new algorithm is presented which offers significant advantages of speed and storage utilization. The routine for implementing this algorithm can be written in the list language with which it is to be used, thus insuring a degree of machine independence. Finally, the application of the algorithm to a number of different list structures appearing in the literature is indicated.

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Research and Advances

A note on the formation of free list

The concept of an available-space list was introduced by Newell and Shaw [1] in 1957, and has since been incorporated into a number of different systems [2-5]. The available-space list (or “free list”) is a list of all available memory locations. It should initially be as large as possible, and ideally it would contain every cell not used by the program. The subject of this note is the initial formation of a free list on the IBM 7090-7094, using the FORTRAN II monitor, version 2. The method presented originated while the authors were working on an implementation of the WISP [5] system for the 7090 in cooperation with Prof. M. V. Wilkes and his colleagues.

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