41.c

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#include <stdio.h>
#include <stdlib.h>

void main(int argc,char *argv[])
{
	FILE *fp1,*fp2;
	char c,ch;
	long j;
    if(argc != 3) exit(0);
	fp1 = fopen(argv[1],"rb");/*打开文件供读*/
	fp2 = fopen(argv[2],"wb");/*打开文件供写*/
	if((fp1 == NULL)||(fp2 == NULL))
	{
		printf("cannot open file\n");
	    exit(1);
	}
	printf("请输入密码：");
	scanf("%i",&j);
	srand(j);/*初始化随机数发生器*/
	ch = fgetc(fp1);/*ch为文件字符流*/
	while(!feof(fp1))
	{
		c = rand();/*c为随机字符流*/
	    ch = ch ^ c;/*异或加密*/ 
		fputc(ch,fp2);
        ch = fgetc(fp1);
	}
    fclose(fp1);
	fclose(fp2);
	exit(0);
}