All of them are POSIX-compliant. All present similar command-line interfaces to their users. All use kernels and system libraries that make similar programming models and application usage characteristics possible.

• 所有这些操作系统分支都符合POSIX,都为它们的用户呈现了一个类似的命令行界面,并且都使用了使编程模式与应用程序用法特征尽可能类似的内核和系统库。