程序代码：

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#define MAX 30
void copy(FILE * fp1,FILE * fp2);
int main(void)
{
    char rce_file[MAX],tar_file[MAX];                  //  储存源文件和目标文件的文件名
    FILE * fp1,* fp2;                                                 //  两个文件指针
    char ch;

    printf("input name of source file: ");
    gets(rce_file);
    strcat(rce_file,".txt");                                      //  打开的是文本文档
    printf("input name of target file: ");
    gets(tar_file);
    strcat(tar_file,".txt");
    if((fp1 = fopen(rce_file,"rb")) == NULL)       //  只读二进制模式
    {
        printf("can't open %s file",rce_file);
        exit(1);
    }
    if((fp2 = fopen(tar_file,"a+b")) == NULL)     //  读写二进制模式
    {
        printf("can't open %s file",tar_file);
        exit(2);
    }
    copy(fp1,fp2);                                                //  调试复制函数
    while((ch = getc(fp2)) != EOF)                     //  查看目标文件被复制的内容 （如果这段代码不写就不会出现“屯屯屯屯屯”）
        putc(ch,stdout);
    fclose(fp1);                                                   //  关闭文件
    fclose(fp2);
    system("pause");
    return 0;
}

void copy(FILE * fp1,FILE * fp2)
{
    char copy_s;

    while(EOF != (copy_s = fgetc(fp1)))
        fputc(copy_s,fp2);
}

while((ch = getc(fp2)) != EOF) putc(ch,stdout);