Abstract: In order to implement a small specialized computer aided design （CAD） software system in a microcomputer （IBM-PC is taken for the sample in this paper）, the following problems, must be solved:1.Must a DBMS （Data Base Management System） be used in a small specialzed CAD software system? For a small specilized CAD system the types of the data are not complex,so the DBMS is not necessary. The file management system supported by the OS （Operating System, for example, DOS-Disk Operating System in IBM-PC） can be used to manage the data.2.How to connect the subprogram modules in the CAD system. Each subprogram module can be stored in a disk as a file, and a "menu" is used to invoke these files, The SHELL statement of IBM-PC BASICA is recommended to deal with the connection of the subprograms written in different languages （e.g. FORTRAN or PASCAL） .3.Which interactive language is suitable for our purpose IBM-PC BASICA is the simplest one, Which has graphics functions and sound effects.4.How to establish a graphics data base? Using TREE structure of the file management system supported by IBM-PC DOS. a hierarchical structure of the graphics data base can be constructed. Three methods have been presented to transform the graphics into data file.