This is an optional fixed bar available to an application at all times, whenever core commands are needed.
工具栏是在用户需要使用应用程序时，可以控制该程序核心命令的一个可选的固定工具条。
2
Part III introduced stage bar control system's achieved; this is the core of the system.
第三部分介绍了舞台吊杆控制系统的实现，这是系统的核心部分。
3
It would also be nice if Rich doesn't reserve the vertical bar for anything so we can keep it as part of our core DSL for conditional probability notation.