/in/ex2.c: In function 'main':
/in/ex2.c:6:2: error: implicit declaration of function 'scanf' [-Werror=implicit-function-declaration]
  scanf("%d",&order);
  ^~~~~
/in/ex2.c:6:2: error: incompatible implicit declaration of built-in function 'scanf' [-Werror]
/in/ex2.c:6:2: note: include '<stdio.h>' or provide a declaration of 'scanf'
/in/ex2.c:7:2: error: implicit declaration of function 'whil' [-Werror=implicit-function-declaration]
  whil(scanf("%d",&arr[length])!=EOF){
  ^~~~
/in/ex2.c:7:33: error: 'EOF' undeclared (first use in this function)
  whil(scanf("%d",&arr[length])!=EOF){
                                 ^~~
/in/ex2.c:7:33: note: each undeclared identifier is reported only once for each function it appears in
/in/ex2.c:7:37: error: expected ';' before '{' token
  whil(scanf("%d",&arr[length])!=EOF){
                                     ^
cc1: all warnings being treated as errors