/in/foo.cc:5:21: error: expected ',' or '...' before 'if'
 void dcs(char a,int if);
                     ^
/in/foo.cc: In function 'int main()':
/in/foo.cc:10:6: error: expected unqualified-id before 'if'
  int if=0;
      ^
/in/foo.cc:13:7: error: incompatible types in assignment of 'const char [5]' to 'char [1001]'
   if(a="\\dd\\") break;
       ^
/in/foo.cc:14:6: error: expected primary-expression before 'if'
   if(if!=0) {if=0;cout<<"\\dd\\"<<endl;}
      ^
/in/foo.cc:14:6: error: expected ')' before 'if'
/in/foo.cc:14:16: error: expected '(' before '=' token
   if(if!=0) {if=0;cout<<"\\dd\\"<<endl;}
                ^
/in/foo.cc:15:9: error: expected primary-expression before 'if'
   dcs(a,if);
         ^
/in/foo.cc: At global scope:
/in/foo.cc:21:21: error: expected ',' or '...' before 'if'
 void dcs(char a,int if)
                     ^
/in/foo.cc: In function 'void dcs(char, int)':
/in/foo.cc:25:21: error: invalid conversion from 'char' to 'const char*' [-fpermissive]
  for(i=0;i<=strlen(a)/2;i++)
                     ^
In file included from /usr/include/c++/5/cstring:42:0,
                 from /in/foo.cc:2:
/usr/include/string.h:394:15: note:   initializing argument 1 of 'size_t strlen(const char*)'
 extern size_t strlen (const char *__s)
               ^
/in/foo.cc:25:11: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(i=0;i<=strlen(a)/2;i++)
           ^
/in/foo.cc:27:9: error: invalid types 'char[int]' for array subscript
   if(a[i]!=a[strlen(a)-1+i]) 
         ^
/in/foo.cc:27:22: error: invalid conversion from 'char' to 'const char*' [-fpermissive]
   if(a[i]!=a[strlen(a)-1+i]) 
                      ^
In file included from /usr/include/c++/5/cstring:42:0,
                 from /in/foo.cc:2:
/usr/include/string.h:394:15: note:   initializing argument 1 of 'size_t strlen(const char*)'
 extern size_t strlen (const char *__s)
               ^
/in/foo.cc:27:27: error: invalid types 'char[size_t {aka long unsigned int}]' for array subscript
   if(a[i]!=a[strlen(a)-1+i]) 
                           ^
/in/foo.cc:33:17: error: expected '(' before '=' token
  if(flag==1) {if=1;cout<<a<<endl;}
                 ^
/in/foo.cc:23:8: warning: unused variable 'j' [-Wunused-variable]
  int i,j;
        ^