谁可以给我一个产生随机产生字母（小写）的程序，C语言写的，然后写进文件里，八个字母为一行？谢谢了，

#include <stdio.h>
void main(void)
{
int num;
int i=0;
char ch;
FILE *fp;
char filename[30];
printf("\n\n\nplease input the number of you want:");
scanf("%d",&num);
printf("Please input the file name of you want to save(*.txt):");
scanf("%s%c",filename,&ch);
fp=fopen(filename,"w+"); /* Create file */
if(fp==NULL)
printf("Con't create the file %s!!!!",filename);
/*rand some letter*/
for(i=1; i<=num; i++)
{
ch=rand()%26+'a';
printf("%c ",ch);
fprintf(fp,"%c ",ch);
if(i%8==0){
printf("\n");
fprintf(fp,"\n");
}
}

fclose(fp);

}