C语言中的while循环中的i ++和++ i有什么区别

Question

我知道i ++表示先返回i，然后加1，而++ i表示先加1，然后返回i。在此代码中：

int isTotalAlphabetical(char word[]){
int i = 0;
while (word[i] != '\0') {
    printf("The %dth is: %d, the char is %c\n", i,isalpha(word[i]), word[i]);
    if (!isalpha(word[i])){
        printf("now return 0, because the %c is not alpha, it's the %d char\n", word[i], i);
        return 0;
    }
    i++;

}
return 1;

}

在此循环中，当我将i ++移至“ while（word [i ++]！='\ 0'）”时，输出将打印出以下信息

The 2th is: 1, the char is p
The 3th is: 1, the char is l
The 4th is: 1, the char is e
The 5th is: 0, the char is 
now return 0, because the  is not alpha, it's the 5 char

当我将++ i移至“ while（word [++ i]！='\ 0'）”时，输出将忽略第一个字符。它显示：

The 1th is: 1, the char is p
The 2th is: 1, the char is p
The 3th is: 1, the char is l
The 4th is: 1, the char is e

那怎么可能？