/in/foo.c:30:6: warning: return type of 'main' is not 'int' [-Wmain]
 void main()
      ^~~~
/in/foo.c: In function 'main':
/in/foo.c:32:12: error: expected expression before 'char'
    encrypt(char a,char b);
            ^~~~
/in/foo.c:32:4: error: too few arguments to function 'encrypt'
    encrypt(char a,char b);
    ^~~~~~~
/in/foo.c:18:6: note: declared here
 void encrypt(char a[],char b[])
      ^~~~~~~
/in/foo.c:31:16: warning: unused variable 'a' [-Wunused-variable]
 {  static char a[30]="No.1",b[100];
                ^
At top level:
/in/foo.c:31:16: warning: 'a' defined but not used [-Wunused-variable]