1. A virtual machine system for computer code behavior analysis of a target program, the virtual machine system operating within a host real computer system having a software processor comprising: a behavior record storing behavior flags representative of computer code behavior observed by virtually executing the computer code of the target program under analysis within the virtual machine system; a sequencer that stores a sequence in which behavior flags are set and reset in the behavior record during virtual execution of the computer code of the target program under analysis; and simulated memory automatically configured with a map of the virtual machine system comprising assigned areas for receiving predetermined types of data from the target program based on a file format of the target program; and a simulated operating system representative of a host real computer system, the simulated operating system comprising one or more layered operating system shells that correspond with the memory map so that the virtual machine system is capable of executing DOS target programs, the computer code of the target program under analysis interacting with the simulated memory and the simulated operating system to generate the behavior flags, wherein the virtual machine system passes data representative of the behavior record to the host real computer system prior to termination of the virtual machine system.