C程序参考,简单易懂,是初学者不可少的参考资料

				#include
				#include
				void main()
				{  FILE *fp;char  ch;
				   if((fp=fopen("d:\\a1.txt","r+"))==NULL)
				   {   printf("Cann't Open File d:\\a1.txt");
				       exit(0);
				   }
				ch=fgetc(fp);
				   while(!feof(fp))
				   {  if(ch>='A'&&ch				      else if(ch>='a'&&ch				      else if(ch>='0'&&ch				      fseek(fp,-1L,1);
				      fputc(ch,fp);
				fseek(fp,0L,1);
				ch=fgetc(fp);
				   }
				   fclose(fp);
				}