返回：贺老师课程教学链接

1、阅读下面的程序，写出输出结果，并上机运行程序进行对照

#include "stdio.h"
int main()
{
    FILE *outfile,*infile;
    outfile=fopen("data.dat","w");
    fprintf(outfile, "1111111111\n");
    fprintf(outfile, "aaaaaaaaaa\n");
    fprintf(outfile,"AAAAAAAAAA\n");
    fprintf(outfile,"**********\n");
    fclose(outfile);
    infile=fopen("data.dat","r");
    char line[80];
    int i=0;
    while(!feof(infile))
    {
        i++;
        fgets(line,sizeof(line), infile);
        printf("%d: %s", i, line);
    }
    fclose(infile);
    return 0;
}

2、区分ASCII文件和二进制文件：阅读并运行下面的两个程序，分别用记事本和二进制文件阅读器（请自行下载Binary Viewer等程序，或者用DOS中的Debug程序，并百度其用法）。查看其内容，并理解文件存储的原理。
（1）

#include <stdio.h>
#include <stdlib.h>
int main()
{
    FILE *outfile;
   int a;
    outfile=fopen("f1.dat","w");
    if(!outfile)
    {
        printf("open error!\n");
        exit(1);
    }
    scanf("%d", &a);
    fprintf(outfile, "%d", a);
    fclose(outfile);
    return 0;
}

（2）

#include <stdio.h>
#include <stdlib.h>
int main()
{
    FILE *outfile;
   int a;
    outfile=fopen("f2.dat","wb");
    if(!outfile)
    {
        printf("open error!\n");
        exit(1);
    }
    scanf("%d", &a);
    fwrite(&a, sizeof(int), 1, outfile);
    fclose(outfile);
    return 0;
}

3、阅读下面的程序，指出其功能，体会fseek()等与文件指针相关的函数的功能及其用法
（1）请说出程序的输出

#include <stdio.h>
#include <stdlib.h>
char *filename = "a.txt";
int main()
{
    FILE *file;
    long l,m;
    file=fopen(filename,"rb");
    if(!file)
    {
        printf("open error!\n");
        exit(1);
    }
    l = ftell(file);  //ftell函数返回文件位置指针相对于文件首的偏移量
    fseek(file, 0, SEEK_END);
    m = ftell(file);
    fclose(file);
    printf("size of %s is %ld bytes.\n", filename, (m-l));
    return 0;
}

（2）请说出运行程序后test.txt中的内容

#include <stdio.h>
#include <stdlib.h>
int main()
{
    FILE *outfile;
    long pos;
    outfile=fopen("test.txt","w");
    if(!outfile)
    {
        printf("open error!\n");
        exit(1);
    }
    fwrite ("This is an apple",16, 1, outfile);
    pos=ftell(outfile);
    fseek(outfile, pos-7, SEEK_SET);
    fwrite (" sam", 4, 1, outfile);
    fclose(outfile);
    return 0;
}