/in/foo.c:1:9: error: #include expects "FILENAME" or <FILENAME>
 #include
         ^
/in/foo.c: In function 'main':
/in/foo.c:5:1: warning: implicit declaration of function 'scanf' [-Wimplicit-function-declaration]
 scanf("%c",&c1);
 ^~~~~
/in/foo.c:5:1: warning: incompatible implicit declaration of built-in function 'scanf'
/in/foo.c:5:1: note: include '<stdio.h>' or provide a declaration of 'scanf'
/in/foo.c:7:1: warning: implicit declaration of function 'printf' [-Wimplicit-function-declaration]
 printf("大写字符%c对应的小写字母是%c,小写字符的ASCII是%d",c1,c2,c2);
 ^~~~~~
/in/foo.c:7:1: warning: incompatible implicit declaration of built-in function 'printf'
/in/foo.c:7:1: note: include '<stdio.h>' or provide a declaration of 'printf'