一個密碼的小程式問題

enter

#include <stdio.h>
#include <conio.h>
#include <string.h>
int main(void)
{
char pw[15],pw1[15];
int x;

printf("Enter password  5 characters:\n");

for(x=0;x<5;x++){
pw[x]=getch();
  }
pw[5]='\0';
printf("Re-enter your password again:");
for(x=0;x<5;x++){
pw1[x]=getch();
  }
pw1[5]='\0';

if(strcmp(pw,pw1))
{
printf("Do not match.\n");

do{
printf("Please enter your password again.\n");
for(x=0;x<5;x++)
{
pw1[x]=getch();

}}while(strcmp(pw,pw1));
}
printf("Your password is %s.\n",pw);

return 0;
}


問題主要在於我的輸入函數得用getch()才行，如果使用getchar()，則很奇怪的，pw() or pw1()中有一個的字串會少或多一個字符，而造成pw pw1二者肯定不同。為何會這樣呢？

enter

#include <stdio.h>
#include <conio.h>

int main(void){

char s[10],t[10];

printf("enter password,no more than 5 characters:\n");
gets(s);

while(s[5]) //這裡若用 while(strlen(s)>=5) 則本題ok，所以while(s[5])有何邏輯上的錯誤呢？
{
printf("too many characters,enter again:\n"); //一旦第一次多於五個字符，後面就算再輸入三個，它也顯示too many。似乎要剛好輸入五個字符才ok。不知是何原因？
gets(s);
}

printf("enter again:\n");
gets(t);


while(strcmp(s,t))
{
printf("not match! enter again:\n");
gets(t);
}

return 0;
}

enter

#include <stdio.h>

int main(void){
char pw[10],pw1[10];

printf("Please enter your password,no less than 3 and no more than 8 characters:\n");
gets(pw);

while(strlen(pw)<3||strlen(pw)>8)
{
if(strlen(pw)<3)
{
  printf("Sorry, too few, try again:\n");
  gets(pw);
  }
if(strlen(pw)>8)
{
printf("Sorry,too many, try again:\n");
gets(pw);
}
}

printf("Please enter your password again:\n");
gets(pw1);
while(strcmp(pw,pw1) )
{
printf("Sorry, your password not match!\n Re-enter again:\n");
gets(pw1);
}

printf("Your password is %s.\n",pw);

return 0;
}

enter

#include <stdio.h>

int main(void)
{
char pw[20],pw1[20];
int x;
printf("Please choose your password for 4 to 8 characters, press ENTER to finish:\n");
x=0; \\初始化成0
do{
pw[x]=getch();
printf("*");
x++;
}
while(pw[x-1]!='\r'); \\因為x已經++到下一個去了。
pw[x-1]='\0'; \\字串要收尾，否則後面陣列中可能還有其他先前已輸入的值。
  
while((strlen(pw)<4)||(strlen(pw)>8))
{
  
while(strlen(pw)>8)
{
printf("Too many, please choose again:\n");
   x=0;
   
   do{
   pw[x]=getch();
   printf("*");
   x++;
   }  while(pw[x-1]!='\r');
   pw[x-1]='\0';
   
}
while(strlen(pw)<4)
   {
     printf("Too few, please choose more:\n");
     x=0;
     do{
     pw[x]=getch();
     printf("*");
     x++;
     }   while(pw[x-1]!='\r');
     pw[x-1]='\0';
}
}
  
printf("\nPlease re-enter your password:\n");
x=0;

do{
pw1[x]=getch();
printf("*");
x++;} while(pw1[x-1]!='\r');
pw1[x-1]='\0';
while(strcmp(pw,pw1)){
   printf("Sorry, password nit match.Please enter again:\n");
   x=0;

do{
pw1[x]=getch();
printf("*");
x++;} while(pw1[x-1]!='\r');
pw1[x-1]='\0';
}

printf("Your password is %s\n",pw);

return 0;
}