/in/foo.c: In function 'en':
/in/foo.c:11:5: error: subscripted value is neither array nor pointer nor vector
    s[i++]=t+'0';
     ^
/in/foo.c:13:5: error: subscripted value is neither array nor pointer nor vector
    s[i++]=t-10+'A';
     ^
/in/foo.c:16:3: error: subscripted value is neither array nor pointer nor vector
  s[i]='\0';
   ^
/in/foo.c:18:9: error: subscripted value is neither array nor pointer nor vector
   temp=s[i],s[i]=s[t],s[t]=temp;
         ^
/in/foo.c:18:14: error: subscripted value is neither array nor pointer nor vector
   temp=s[i],s[i]=s[t],s[t]=temp;
              ^
/in/foo.c:18:19: error: subscripted value is neither array nor pointer nor vector
   temp=s[i],s[i]=s[t],s[t]=temp;
                   ^
/in/foo.c:18:12: warning: left-hand operand of comma expression has no effect [-Wunused-value]
   temp=s[i],s[i]=s[t],s[t]=temp;
            ^
/in/foo.c:18:24: error: subscripted value is neither array nor pointer nor vector
   temp=s[i],s[i]=s[t],s[t]=temp;
                        ^
/in/foo.c:18:22: warning: left-hand operand of comma expression has no effect [-Wunused-value]
   temp=s[i],s[i]=s[t],s[t]=temp;
                      ^
/in/foo.c: In function 'encrypt':
/in/foo.c:27:16: warning: passing argument 3 of 'en' makes integer from pointer without a cast [-Wint-conversion]
    en(a[i]+5,8,s);
                ^
/in/foo.c:3:6: note: expected 'char' but argument is of type 'char *'
 void en(char c,int n,char s)
      ^~
/in/foo.c:29:17: warning: passing argument 3 of 'en' makes integer from pointer without a cast [-Wint-conversion]
    en(a[i]-5,16,s);
                 ^
/in/foo.c:3:6: note: expected 'char' but argument is of type 'char *'
 void en(char c,int n,char s)
      ^~
/in/foo.c: At top level:
/in/foo.c:34:6: warning: return type of 'main' is not 'int' [-Wmain]
 void main()
      ^~~~
/in/foo.c: In function 'main':
/in/foo.c:37:10: error: expected expression before 'char'
  encrypt(char a[30],char b[30]);
          ^~~~
/in/foo.c:37:2: error: too few arguments to function 'encrypt'
  encrypt(char a[30],char b[30]);
  ^~~~~~~
/in/foo.c:20:6: note: declared here
 void encrypt(char a[],char b[])
      ^~~~~~~
/in/foo.c:36:14: warning: unused variable 'a' [-Wunused-variable]
  static char a[30]="No.1",b[100];
              ^
At top level:
/in/foo.c:36:14: warning: 'a' defined but not used [-Wunused-variable]