The three elements of till type structure are loop body, loop variable and loop termination condition. These three elements are indispensable to a complete until cycle structure.

UNTIL the structure (until) format is as follows:

do

& lt loop statement group >;

Loop until < loop termination condition >;

Execute the loop body statement group first, test the loop termination condition when executing the loop statement, continue to execute the loop body statement group when the loop condition is false, and terminate the loop until the loop termination condition becomes true.

UNTIL loop is to execute the loop body first, and then judge whether the condition is true. If the condition is not true, the DO statement is returned to execute the loop body again, and if the condition is true, the loop is exited. The loop body is executed at least once until the program of type I loop structure runs.

Extended data

There are two kinds of loop structures, which are divided into when loop and till loop.

When the loop is executed, the control conditions are judged first, and the loop is executed again when the conditions are met, and stopped when the conditions are not met; Until the loop is executed once, and then the control conditions are judged. Execute the loop when the condition is not met, and stop when the condition is met.

The difference between the two cycles is that the cycle is judged first, and then the cycle is judged; Until the loop is executed once, then judge whether to continue the loop; The type loop is executed when the condition is met, and the loop body is not executed until the type loop is not met.

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