结构化程序goto语句

Program 1:

程序1：

#include <iostream>
#include <math.h>
using namespace std;
int main()
{
int num1 = 1;
int num2 = 0;
MY_LABEL:
num2 = num1 * num1;
cout << num2 << " ";
num1 = num1 + pow(2, 0);
if (num1 <= 5)
goto MY_LABEL;
return 0;
}

Output:

输出：

1 4 9 16 25

Explanation:

说明：

The above code will print "1 4 9 16 25" on the console screen.

上面的代码将在控制台屏幕上显示“ 1 4 9 16 25” 。

Understand the program step by step.

逐步了解程序。

Here we initialize the variables num1 and num2 by 1, 0 respectively.  And we created a label MY_LABEL.

在这里，我们分别将变量num1和num2初始化为1、0。 然后我们创建了标签MY_LABEL 。

Now evaluate statements iteration wise:

现在，明智地评估语句迭代：

First iteration:

第一次迭代：

num1=1, num2=0
num2 = num1 * num1;
Then num1 = 1 and num2 = 1 and then print num2 that is 1.
As we know that if we calculate the 
zero power of any number that will be 1.
num1 = num1 + pow(2,0);
Then the above statement will increase the value of num1 by one. 
Then num1 become 2. 
And num1 is less than equal to 5 then "goto" statement 
will transfer the program control to the MY_LABEL.

Second iteration:

第二次迭代：

num1=2, num2=0
num2 = num1 * num1;
After execution of above statement, 
num1=2 and num2=4 and then print num2 that is 4
num1 = num1 + pow(2,0);
Then above statement will increase the value of num1 by one. 
Then num1 become 3. 
And num1 is less then equal to 5 then "goto” statement 
will transfer the program control to the MY_LABEL.

Third Generation:

第三代：

num1=3, num2=0
num2 = num1 * num1;
After execution of above statement, 
num1=3 and num2=9 and then print num2 that is 9
num1 = num1 + pow(2,0);
Then above statement will increase the value of num1 by one. 
Then num1 become 4. 
And num1 is less then equal to 5 then "goto" statement 
will transfer the program control to the MY_LABEL.

Fourth iteration:

第四次迭代：

num1=3, num2=0
num2 = num1 * num1;
After execution of above statement, 
num1=4 and num2=16 and then print num2 that is 16
num1 = num1 + pow(2,0);
Then above statement will increase the value of num1 by one. 
Then num1 become 5. 
And num1 is less then equal to 5 then "goto" statement 
will transfer the program control to the MY_LABEL.

Fifth iteration:

第五次迭代：

num1=3, num2=0
num2 = num1 * num1;
After execution of above statement, 
num1=5 and num2=25 and then print num2 that is 25
num1 = num1 + pow(2,0);
Then above statement will increase the value of num1 by one. 
Then num1 become 6. 
Then condition get false and program get terminated.

Program 2:

程式2：

#include <iostream>
#include <math.h>
using namespace std;
int main()
{
int num1 = 1;
int num2 = 0;
int num3 = 1;
MY_LABEL:
num3 = num3 + num2;
cout << num3 << " ";
num2 = num2 + 1;
num1 = num1 + 1;
if (num1 <= 4)
goto MY_LABEL;
return 0;
}

Output:

输出：

1 2 4 7

Explanation:

说明：

The above code will print "1 2 4 7" on the console screen.

上面的代码将在控制台屏幕上显示“ 1 2 4 7” 。

Understand the program step by step.

逐步了解程序。

Here we initialize the variables num1, num2, and num3 by 1, 0, and 1 respectively.  And we created a label MY_LABEL.

在这里，我们分别将变量num1 ， num2和num3分别初始化为1、0和1。 然后我们创建了标签MY_LABEL 。

Now evaluate statements iteration wise:

现在，明智地评估语句迭代：

First iteration:

第一次迭代：

Here initial values of num1=1, num2 =0, and num3 =1 
after executing all statements "1" will be printed on 
console screen and modified value will be:
num1 = 2, num2 = 1, num3= 1;
If the condition is true then program control 
will be transferred to MY_LABEL.

Second iteration:

第二次迭代：

Here values of num1=2, num2 =1, and num3 =1 
after executing all statements "2" will be printed on 
console screen and modified value will be:
num1 = 3, num2 = 2, num3= 2;
If the condition is true then program control 
will be transferred to MY_LABEL.

Third iteration:

第三次迭代：

Here values of num1=3, num2 =2, and num3 =2 
after executing all statements "4" will be printed on 
console screen and modified value will be:
num1 = 4, num2 = 3, num3= 4;
If the condition is true then program control 
will be transferred to MY_LABEL.

Fourth iteration:

第四次迭代：

Here values of num1=4, num2 =3, and num3 =4 
after executing all statements "7” will be printed on 
console screen and modified value will be:
num1 = 4, num2 = 4, num3= 7;
Now the if condition gets false and the program will terminate.

翻译自: https://www.includehelp.com/cpp-tutorial/goto-statement-find-output-programs-set-1.aspx

结构化程序goto语句