stdout,stdin浅析

《The C programming Language》     stdin,stdout 
"The file pointers stdin and stdout are objects of type FILE *. They are constants, however, not variables, so it is not possible to assign to them."
stdout               printf    fprintf         stdout              ，            (  )       ，              ，                       . C        stdout           。
#include <stdio.h>
int main(int argc,char *argv[])
{
	FILE *ifile;
	//FILE *ofile;
	char c;
	if(argc <= 1)
	{
		return 0;
	}
	else
	{
		if((ifile = fopen(*++argv,"r")) == NULL)
		{
			printf("cat the file %s erro.
",*argv);
			return 0;
		}
		else
		{
			while((c = getc(ifile)) != EOF)
			{
				putc(c,stdout);
			}
		}

	}
	return 0;
}