程序由指令段或指令块组成，它们在需要之前一直处于空闲状态。需要时，程序移动到适当的部分以完成任务。当一段代码繁忙时，其他部分处于非活动状态。控制语句是程序员指示在特定时间使用哪些代码段的方式。

控制语句是源代码中控制程序执行流的元素。它们包括使用{和}括号的块，使用for、while和do-while的循环，以及使用if和switch的决策。还有后藤。有两种类型的控制语句：条件语句和无条件语句。

C++中的条件语句

有时，程序需要根据特定条件执行。当满足一个或多个条件时，执行条件语句。这些条件语句中最常见的是if语句，其形式如下：

This statement executes whenever the condition is true.

C++ uses many other conditional statements including:

• if-else: An if-else statement operates on an either/or basis. One statement is executed if the condition is true; another is executed if the condition is false.
• if-else if-else: This statement chooses one of the statements available depending on the condition. If no conditions are true, the else statement at the end is executed.
• while: While repeats a statement as long as a given statement is true.
• do while: A do while statement is similar to a while statement with the addition that the condition is checked at the end.
• for: A for statement repeats a statement as long as the condition is satisfied.

Unconditional Control Statements

Unconditional control statements do not need to satisfy any condition. They immediately move control from one part of the program to another part. Unconditional statements in C++ include:

• goto: A goto statement directs control to another part of the program.
• break: A break statement terminates a loop (a repeated structure) 
• continue: A continue statement is used in loops to repeat the loop for the next value by transferring control back to the beginning of the loop and ignoring the statements that come after it.