void main()

{

int a=0,s=0,b;

char password[10];

char key[10]="cdw#";

do

{ a++;

printf("請輸入密碼");

printf("\n");

gets(password);

if(strcmp(password,key)==0)

{printf("密碼正確,歡迎使用");

s=1;}

if(strcmp(password,key)!=0)

printf("密碼錯誤! ");

}

while(s==0&&a<3);

if(s==0)

printf("輸入密碼超過次數");

if(s==1)

{printf("歡迎使用\n");

printf("**********************************************\n");

printf("* 1----加法 *\n");

printf("* 2----減法 *\n");

printf("* 3----乘法 *\n");

printf("* 4----除法 *\n");

printf("* 5----求餘 *\n");

printf("* 6----階乘 *\n");

printf("* 7----累加 *\n");

printf("* 8----結束 *\n");

printf("**********************************************\n");

printf("請選擇一種運算\n");

scanf("%d",&b);

if(b==1)

{int number1,number2;

int sum;

printf("請輸入兩個數:");

scanf("%d %d", &number1,&number2);

sum= number1+number2;

printf("%d+%d=%d\n", number1,number2,sum);}

else if(b==2)

{ int number1,number2;

int subtraction;

printf("請輸入兩個數:");

scanf("%d %d", &number1,&number2);

subtraction= number1-number2;

printf("%d-%d=%d\n", number1,number2,subtraction);}

else if(b==3)

{int number1,number2;

int multiplication;

printf("請輸入兩個數:");

scanf("%d %d", &number1,&number2);

multiplication= number1*number2;

printf("%d*%d=%d\n", number1,number2,multiplication);}

else if(b==4) { int number1,number2;

int division;

printf("請輸入兩個數:");

scanf("%d %d", &number1,&number2);

division= number1/number2;

printf("%d*%d=%d\n", number1,number2,division);}

else if(b==5)

{ int number1,number2;

int complementation;

printf("請輸入兩個數:");

scanf("%d %d", &number1,&number2);

complementation=number1%number2;

printf("%d%%%d=%d\n", number1,number2,complementation);

}

else if(b==6)

{int number1,i=0,factorial=1;

scanf("%d",&number1);

while(i<number1)

{i++;

factorial=factorial*i;

}

printf("%d!=%d",number1,factorial);

}

else if(b==7)

{int number1,i=0,add=0;

scanf("%d",&number1);

while(i<number1)

{i++;

add=add+i;

}

printf("%d+....+%d=%ds",1,number1,add);

}

else if(b==8)

printf("結束,歡迎下次使用");

else

printf("不在能力範圍");}

else

printf("密碼錯誤,請重試\n");

}

字串輸入：

•(1)gets函式形式為“gets(str);”

•(2)scanf函式，形式為“scanf(“%s”,str);”

注意：

      用gets輸入字串時，只有遇到回車符才認為字串輸入完畢；而用scanf輸入字串時，遇到空格、跳格符或回車符都認為字串輸入完畢。

printf("%d%%%d=%d\n", x%y ); 求餘的時候要加兩個%