Question

C语言中，编程实现将文本文件file1.dat中的内容复制到文本文件file2.dat中去，同时将小写字母转换成大写字

Answer 1

#include "stdio.h"
#include <stdlib.h>
void main()
{
FILE *in,*out;
char ch;

if((in=fopen("file1.dat","r+"))==NULL)
{
printf("can,t open thie file!");
exit(0);
}
if((out=fopen("file2.dat","w+"))==NULL)
{
printf("can,t open thie file!");
exit(0);
}

while(!feof(in))
{
ch=fgetc(in);
char ch1=ch+'A'-'a';
fputc(ch1,out);//从infile中取入字符放到outfile文件中去

}
while(!feof(out))
{

ch=fgetc(out);

putchar(ch);
out++;
}
fclose(in);
fclose(out);

}

Answer 2

#include "stdio.h"
main()
{
FILE *fp1,*fp2;
char ch;
if((fp1=fopen("file1.dat","rb"))==NULL)
{
printf("Can't open file1.dat!\n");
return;
}
if((fp2=fopen("file2.dat","wb"))==NULL)
{
printf("Can't open file2.dat!\n");
return;
}
while(!feof(fp1))
{
ch=fgetc(fp1);
if(ch>='a'&&ch<='z') ch-='a'-'A';
if(ch!=-1) fputc(ch,fp2);
}

fcloseall();

}

Answer 3

引用heartfleet的回答：
#include "stdio.h"
#include <stdlib.h>
void main()
{
FILE *in,*out;
char ch;

if((in=fopen("file1.dat","r+"))==NULL)
{
printf("can,t open thie file!");
exit(0);
}
if((out=fopen("file2.dat","w+"))==NULL)
{
printf("can,t open thie file!");
exit(0);
}

while(!feof(in))
{
ch=fgetc(in);
char ch1=ch+'A'-'a';
fputc(ch1,out);//从infile中取入字符放到outfile文件中去

}
while(!feof(out))
{

ch=fgetc(out);

putchar(ch);
out++;
}
fclose(in);
fclose(out);

}

不用return 0？