What differentiates an executable unit from a basic block is the condition that triggers the end of the executable unit.

可执行的单元与基本块的不同点，在于决定一个可执行单元末尾的因素。

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An executable unit begins at the start of every basic block and at any instruction that corresponds to a line of source code that is different than the previous instruction.

一个可执行的单元由每一个基本快开始，而与每行源代码相对应的指南与前面版本中的指南有所不同。

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The arguments above specify an expression that yields a boolean value and a block of code that returns nothing (Unit), which is exactly what while expects.

上述语句指定了一个表达式，该表达式产生了一个布尔值和一个不返回任何结果的代码块（Unit），这正是 while 所期望的。

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