#include <stdio.h>
#include <string.h>

void find_keyword(char *str)
{
    char *keyword[] = {"IF", "WHERE", "WHEN", "WHILE", "ELSE", "FOR"};
    int i;
    while(*str != 0)
    {
        for(i = 0; i < 6; i++)
        {
            if(!strncmp(str, keyword[i], strlen(keyword[i])))
            {
                printf("存在关键字%s\n", keyword[i]);
            }
        }
        str++;
    }

}

int main()
{
    char str[1000];
    printf("请输入一段英文字母:\n");
    scanf("%s", str);
    find_keyword(str);
}