晶文摘
(夏肇毅 製圖)
作者:夏肇毅 2010-12-16 初版
要根據不同狀況
叫電腦做不同的事
就要用 IF 判斷
如果 "If 判斷式 Then" 判斷式正確
那就會往下執行
否則
就會找下個 "ElseIf ...Then" 繼續判斷
如果還是不對
那就只好執行 "Else" 以後的指令了
如果沒有 "Else"
那就會執行 End If 以後的指令
BASIC之外的語言
會用 "{...}" 把一串指令包成一組
如果要執行的話 就執行這一整組指令
BASIC:
' *******************************************
' Condition statement (If..ElseIf..Else..End If)
' *******************************************
Sub IfStatement()
Dim dPara1 as Double
Dim dPara2 as Double
dPara1 = 1.0
dPara2 = 2.0
' Condition statement (If..ElseIf..Else..End If)
If dPara1 > dPara2 Then
' Is Greater Than
Debug.Print " ";"dPara1 > dPara2";
Debug.Print
ElseIf dPara1 = dPara2 Then
' Equals to
Debug.Print " ";"dPara1 ==dPara2";
Debug.Print
ElseIf dPara1 < dPara2 Then
' Is Less Than
Debug.Print " ";"dPara1 < dPara2";
Debug.Print
End If
If dPara1 <> dPara2 Then
' not equal to
Debug.Print " ";"dPara1 <> dPara2";
Debug.Print
End If
' And Logic
If dPara1 > dPara2 AND dPara1 = dPara2 Then
Debug.Print " ";"dPara1 >=dPara2";
Debug.Print
' Or Logic
ElseIf dPara1 > dPara2 OR dPara1 < dPara2 Then
Debug.Print " ";"dPara1 <> dPara2";
Debug.Print
End If
End Sub
C++:
/* ******************************************* */
/* Condition statement (If..ElseIf..Else..End If) */
/* ******************************************* */
void IfStatement() {
double dPara1;
double dPara2;
dPara1 = 1.0;
dPara2 = 2.0;
/* Condition statement (If..ElseIf..Else..End If) */
if (dPara1 > dPara2) {
/* Is Greater Than */
printf(" %s" , "dPara1 > dPara2");
printf("\n\r" );
} else if (dPara1 ==dPara2) {
/* Equals to */
printf(" %s" , "dPara1 ==dPara2");
printf("\n\r" );
} else if (dPara1 < dPara2) {
/* Is Less Than */
printf(" %s" , "dPara1 < dPara2");
printf("\n\r" );
}
if (dPara1 != dPara2) {
/* not equal to */
printf(" %s" , "dPara1 <> dPara2");
printf("\n\r" );
}
/* And Logic */
if (dPara1 > dPara2 && dPara1 ==dPara2) {
printf(" %s" , "dPara1 >=dPara2");
printf("\n\r" );
/* Or Logic */
} else if (dPara1 > dPara2 || dPara1 < dPara2) {
printf(" %s" , "dPara1 <> dPara2");
printf("\n\r" );
}
}
JAVA:
// *******************************************
// Condition statement (If..ElseIf..Else..End If)
// *******************************************
public void IfStatement() {
double dPara1;
double dPara2;
dPara1 = 1.0;
dPara2 = 2.0;
// Condition statement (If..ElseIf..Else..End If)
if (dPara1 > dPara2) {
// Is Greater Than
System.out.print(" "+"dPara1 > dPara2" );
System.out.println("");
} else if (dPara1 ==dPara2) {
// Equals to
System.out.print(" "+"dPara1 ==dPara2" );
System.out.println("");
} else if (dPara1 < dPara2) {
// Is Less Than
System.out.print(" "+"dPara1 < dPara2" );
System.out.println("");
}
if (dPara1 != dPara2) {
// not equal to
System.out.print(" "+"dPara1 <> dPara2" );
System.out.println("");
}
// And Logic
if (dPara1 > dPara2 && dPara1 ==dPara2) {
System.out.print(" "+"dPara1 >=dPara2" );
System.out.println("");
// Or Logic
} else if (dPara1 > dPara2 || dPara1 < dPara2) {
System.out.print(" "+"dPara1 <> dPara2" );
System.out.println("");
}
}
C#:
/* ******************************************* */
/* Condition statement (If..ElseIf..Else..End If) */
/* ******************************************* */
public void IfStatement() {
double dPara1;
double dPara2;
dPara1 = 1.0;
dPara2 = 2.0;
/* Condition statement (If..ElseIf..Else..End If) */
if (dPara1 > dPara2) {
/* Is Greater Than */
Console.Write(" "+"dPara1 > dPara2");
Console.WriteLine("");
} else if (dPara1 ==dPara2) {
/* Equals to */
Console.Write(" "+"dPara1 ==dPara2");
Console.WriteLine("");
} else if (dPara1 < dPara2) {
/* Is Less Than */
Console.Write(" "+"dPara1 < dPara2");
Console.WriteLine("");
}
if (dPara1 != dPara2) {
/* not equal to */
Console.Write(" "+"dPara1 <> dPara2");
Console.WriteLine("");
}
/* And Logic */
if (dPara1 > dPara2 && dPara1 ==dPara2) {
Console.Write(" "+"dPara1 >=dPara2");
Console.WriteLine("");
/* Or Logic */
} else if (dPara1 > dPara2 || dPara1 < dPara2) {
Console.Write(" "+"dPara1 <> dPara2");
Console.WriteLine("");
}
}
PHP:
/* ******************************************* */
/* Condition statement (If..ElseIf..Else..End If) */
/* ******************************************* */
function IfStatement() {
$dPara1 = 1.0;
$dPara2 = 2.0;
/* Condition statement (If..ElseIf..Else..End If) */
if ($dPara1 > $dPara2) {
/* Is Greater Than */
echo " "."dPara1 > dPara2";
echo "";
} elseif ($dPara1 ==$dPara2) {
/* Equals to */
echo " "."dPara1 ==dPara2";
echo "";
} elseif ($dPara1 < $dPara2) {
/* Is Less Than */
echo " "."dPara1 < dPara2";
echo "";
}
if ($dPara1 != $dPara2) {
/* not equal to */
echo " "."dPara1 <> dPara2";
echo "";
}
/* And Logic */
if ($dPara1 > $dPara2 && $dPara1 ==$dPara2) {
echo " "."dPara1 >=dPara2";
echo "";
/* Or Logic */
} elseif ($dPara1 > $dPara2 || $dPara1 < $dPara2) {
echo " "."dPara1 <> dPara2";
echo "";
}
}