程序代码：

#include <stdio.h>

int main(void)
{
    int i,flag;
    char str[80],c;
    FILE * fp;

    fp = fopen ("text","w");

    flag = 1;

    while (flag == 1)
    {

        printf ("input string:\n");

        gets(str);

        fprintf (fp,"%s ",str);

        printf ("continue?");

        c = getchar();

        if ((c == 'N')||(c == 'n'))
            flag = 0;
        getchar();
    }

    fclose (fp);

    fp = fopen("text","t");

    while(fscanf(fp,"%s",str) != EOF)
    {
        for (i = 0;str[i]!='\0';i++)
            if ((str[i] >= 'a') && (str[i] <= 'z'))
                str[i] -= 32;

        printf ("%s\n",str);
    }

    fclose (fp);

    return 0;
}