void main()
{
int a=0,s=0,b;
char password[10];
char key[10]="cdw#";
do
{ a++;
printf("请输入密码");
printf("\n");
gets(password);
if(strcmp(password,key)==0)
{printf("密码正确,欢迎使用");
s=1;}
if(strcmp(password,key)!=0)
printf("密码错误! ");
}
while(s==0&&a<3);
if(s==0)
printf("输入密码超过次数");
if(s==1)
{printf("欢迎使用\n");
printf("**********************************************\n");
printf("* 1----加法 *\n");
printf("* 2----减法 *\n");
printf("* 3----乘法 *\n");
printf("* 4----除法 *\n");
printf("* 5----求余 *\n");
printf("* 6----阶乘 *\n");
printf("* 7----累加 *\n");
printf("* 8----结束 *\n");
printf("**********************************************\n");
printf("请选择一种运算\n");
scanf("%d",&b);
if(b==1)
{int number1,number2;
int sum;
printf("请输入两个数:");
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("请输入两个数:");
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("请输入两个数:");
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("请输入两个数:");
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("请输入两个数:");
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("结束,欢迎下次使用");
else
printf("不在能力范围");}
else
printf("密码错误,请重试\n");
}
字符串输入：
•(1)gets函数形式为“gets(str);”
•(2)scanf函数，形式为“scanf(“%s”,str);”
注意：
用gets输入字符串时，只有遇到回车符才认为字符串输入完毕；而用scanf输入字符串时，遇到空格、跳格符或回车符都认为字符串输入完毕。
printf("%d%%%d=%d\n", x%y ); 求余的时候要加两个%