#include main(){ FILE *fp; char ch; //文件名要全,名字本来是"case1.in.txt",而不是"case1.in" if((fp=fopen("case1.in.txt","r"))==NULL) return 0; while((ch=fgetc(fp))!=EOF){ if('A'<=ch&&ch<='Z') ch=ch+32; putchar(ch); } fclose(fp);}