13-8、

#include <stdio.h>

int main(void)
{
    FILE *sfp;
    FILE *dfp;
    int ch;
    char sfilename[FILENAME_MAX];
    char dfilename[FILENAME_MAX];
    printf("Please input the sfilename: "); scanf("%s", sfilename);
    printf("Please input the dfilename: "); scanf("%s", dfilename);
    
    
 
if((sfp = fopen(sfilename, "r")) == NULL)
        printf("\aSource file open failed.\n");
    else
    {
        if((dfp = fopen(dfilename, "w")) == NULL)
            printf("\aDestination file open failed.\n");
        else
        {
            while((ch = fgetc(sfp)) != EOF)
            {
                putchar(ch);
                fputc(ch, dfp);
            }
            fclose(dfp);
        }
        fclose(sfp);
    } 
    
 
return 0;
}

13 - 9、

#include <stdio.h>
#include <ctype.h>

int main(void)
{
    FILE *sfp;
    FILE *dfp;
    int ch;
    char sfilename[FILENAME_MAX];
    char dfilename[FILENAME_MAX];
    printf("Please input the sfilename: "); scanf("%s", sfilename);
    printf("Please input the dfilename: 
 
"); scanf("%s", dfilename);
    
    if((sfp = fopen(sfilename, "r")) == NULL)
        printf("\aSource file open failed.\n");
    else
    {
        if((dfp = fopen(dfilename, "w")) == NULL)
            printf("\aDestination file open failed.\n");
        else
        {
            while((ch = fgetc(sfp)) != EOF)
                fputc(toupper(ch), dfp);
            fclose(dfp);
        }
        fclose(sfp);
    }
    return 0;
}

13-10、

#include <stdio.h>
#include <ctype.h>

int main(void)
{
    FILE *sfp;
    FILE *dfp;
    int ch;
    char sfilename[FILENAME_MAX];
    char dfilename[FILENAME_MAX];
    printf("Please input the sfilename: "); scanf("%s", sfilename);
    printf("Please input the dfilename: "); scanf("%s", dfilename);
    
    if((sfp = fopen(sfilename, "r")) == NULL)
        printf("\aSfilename open failed.\n");
    else
    {
        if((dfp = fopen(dfilename, "w")) == NULL)
            printf("\aDfilename open failed.\n");
        else
        {
            while((ch = fgetc(sfp)) != EOF)
                fputc(tolower(ch), dfp);
            fclose(dfp);
        }
        fclose(sfp);
    }
    return 0;
}