是设计一个能够判断一个任意正整数n(n＞1)是否为素数的算法

VB6,0函数
Private Function CheckNum(ByVal d As Integer) As Boolean
Dim i As Integer
If d < 2 Then
CheckNum = False
ElseIf d = 2 Then
CheckNum = True
Else
CheckNum = True
For i = 2 To Sqr(d)
If d Mod i = 0 Then
CheckNum = False
Exit For
End If
Next i
End If
End Function
C语言
bool CheckNum(int d)
{
int i;
bool f;
if(d