For i = 1 To 100 For j = 2 To a(i) / 2 if a(i) Mod j = 0 The

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For i = 1 To 100 For j = 2 To a(i) / 2 if a(i) Mod j = 0 Then Exit For Next j If j > a(i) / 2
这是一个求素数的程序段的一部分
既然j的取值是 j = 2 To a(i) / 2
为什么后面还有j > a(i) / 2
功能：生成存放素数的数组 b
将数组 b 的元素个数存入变量 num 中（所有变量均已定义）
For i = 1 To 100
For j = 2 To a(i) / 2
If a(i) Mod j = 0 Then Exit For
Next j
If j > a(i) / 2 Then
num = num + 1
b(num) = a(i)
End If
Next i

重点需要理解内循环的含义:
判断a(i)是否素数,只要用2 ...a(i)/2的数能除尽,就不是素数,也就是说,执行Exit For 跳出内循环的数a(i)肯定不是素数i!此时的就j肯定不超过a(i)/2
如果一个数a(i),用2 ...a(i)/2的所有数相除,都不能除尽,该数肯定是素数,分析一下此时内循环在循环终止时的操作,当j=a(i)/2,满足循环条件执行循环内语句,返回循环头,j自动增1,即j=1+a(i)/2.因此,只要j>a(i)/2,a(i)就是素数.
f语句意为:只要j能够除尽i,就退出内循环.如果

For i = 1 To 100 For j = 2 To a(i) / 2 if a(i) Mod j = 0 The Dim a%(3,3),i%,j% For i = 1 To 3 For j = 1 To 3 If j > land a = 0 For i = 1 To 3 For j = 1 To i For k = j To 3 a = a + 1 Private Sub Command1_Click() For i = 1 To 3 For j = i To 1 a For i = 1 To 4 For j = 1 To 5 b(i) = b(i) + a(i,j) Next j Ne for(j=i;j>0;j--) SOS!Private Sub Command1_Click()/s=0/For j=1 To 20/If j Mod J = 10 For I = 1 To J Step 5 I = I + 2 J = J - I Next I Prin vb题,For i=1 to 2 for j=1 to 2 for k=1 to j 为什么For i = 1 To 3 For j = 1 To i For k = j To 3 a = a + 1 Ne vb多重循环试题For i= 1 to 3 for j= 1to i for k= j to 3 a=a+1 next 有如下代码： For i = 1 To 3 For j = 1 To i For k = j To 3 a = a +