Abstract: Tree structure is a nonlinear data structure,whose evolution process is abstract in the program execution.Memory leak happens while applying modification-like operation on it.It is an open challenge for programming beginner to control the evolution of tree structure in the program debugging procedure,especially to debug the error when memory leakage happens.To address this issue,this paper proposes a tree evaluation visualization model(TEVM) to visualize the evolution procedure of tree structure.Two tree structures are obtained after executing a visual debugging step.This paper designs a structure comparison algorithm to obtain their structural difference including leaked tree by transforming tree structure into linear representation.It also designs a tree layout method and computes their positional difference.A visual evaluation sequence is generated with thesestructural diffe-rence and positional difference.At last,it applys the drawing engine to interpret and execute actions of this sequence to visualize the tree structure evaluation dynamically,smoothly and intuitively.The visualization of tree structure helps programming beginner to understand the execution of program relating to tree structure and improves the efficiency of program debugging.TEVM model is applied in the Web AnyviewC,which is a prototype of the integrated development environment for programming trai-ning,and gains an excellent application effect.

Key words: Data structure visualization, Leaked tree, Program debugging process, Tree struct evaluation visualization model, Tree structure