屏蔽处理是隔离电磁场干扰的措施。一般采用良好接地的金属网或罩实现电磁屏蔽，既可防止外来电磁场干扰，又可防止本身电磁场辐射对外界的干扰。
几乎每个现代操作系统都使用基于位屏蔽权限的模型，该模型基于主体和组按主体处理资源控制。
Nearly every modern OS makes use of a bit-masking permission-based model that deals with the control of resources by principals, based on principals and groups.
各种权限都基于屏蔽一个32位整数——示例应用程序和要求至少需要64位才能处理所需的原子权限。
Permissions were based on masking a 32-bit integer — the example application and requirements would have needed at least 64 bits to handle the required atomic permissions.
每个处理器都具有一个64位的权限屏蔽寄存器(Authority Mask Register, AMR)。
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