cd.cpp

加密置换加密方法．能实现加解密的Ｃ程序．

#include<stdio.h>
#include<process.h>

long d_length(FILE*fp)
{
	long curpos,length;

	curpos=ftell(fp);/*求取文件指针的相对于文件开始的相对位置*/
	printf("\n the begin of this file is %Ld\n",curpos);
	fseek(fp,0L,SEEK_END);/*文件指针指向文件末尾*/
	length=ftell(fp);
	printf("\n the end of this file is %Ld\n",length);
	fseek(fp,curpos,SEEK_SET);/*恢复文件指针的初始值*/
	return(length);
}

void main()
{char name[100];
	long d_len;
	FILE*d_fp;
printf("Input a filename:");
	scanf("%s",name);
   if((d_fp=fopen(name,"r"))==NULL)
	{printf("\n open file error\n");
	exit(0);
	}
	d_len=d_length(d_fp);
	printf("the length of %s is %Ld bytes\n",name,d_len);
}