程序代码：

#include<stdio.h>
#include<stdlib.h>
#include<conio.h>
#include<malloc.h>
#include<ctype.h>

typedef struct Stack
{
   char info;
   struct Stack *next;
}Stack;

Stack *start;
Stack *rstart;
Stack *cstart;
Stack *push(Stack *);
Stack *pop(Stack *);
char peer(Stack *);

int isaplha(char c)
{
    if((('a'<=c)&&(c<='z'))||(('A'<=c)&&('Z'>=c))&&(c!=32))
       return 1;
    else
       return 0;
}

char peer(Stack *rec)
{
     if(rec=NULL)
        printf("Stack is empty.");
     else
        return rec->info;
}

int isempty(Stack  *rec)
{
    if(rec=NULL)
       return 1;
    else
       return 0;
}

Stack *push(Stack *rec,char info)
{
      Stack *new_rec;
      new_rec=(Stack *)malloc(sizeof(Stack));
      new_rec->info=info;
      new_rec->next=rec;
      rec=new_rec;
}

Stack *pop(Stack *rec)
{
      Stack *temp;
      if(rec==NULL)
         printf("Stack is empty.");
      else
      {
           temp=rec->next;
           free(rec);
           rec=temp;
      }
      return rec;
}

int main()
{
    char c;
    int flag=0;
    printf("Enter the characters :\n");
    do
    {
        scanf("%c",&c);
        if(isaplha(c))
        {
            start=push(start,c);
            cstart=push(cstart,c);
        }
    }while(c!=13);
    while(!isempty(start))
    {
        rstart=push(start,peer(start));
        start=pop(start);
    }
    while(!isempty(rstart))
    {
       if(toupper(peer(rstart))==toupper(peer(rstart)))
          flag=1;
       else
       {
          flag=0;
          break;
       }
    }
    if(flag==1)
       printf("The string is a palindrome");
    else
       printf("The string is not a palindrome");
      
system("pause");
}