/in/foo.c: In function 'main':
/in/foo.c:6:14: error: 'a' undeclared (first use in this function)
  scanf("%d",&a);
              ^
/in/foo.c:6:14: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:9:14: warning: comparison of constant '10' with boolean expression is always true [-Wbool-compare]
  else if(0<=x<10)
              ^
/in/foo.c:9:11: warning: comparisons like 'X<=Y<=Z' do not have their mathematical meaning [-Wparentheses]
  else if(0<=x<10)
          ~^~~
/in/foo.c:10:13: error: invalid suffix "x" on integer constant
   y=(2*x*x)+4x-5;
             ^~
/in/foo.c:11:15: warning: comparison of constant '25' with boolean expression is always true [-Wbool-compare]
  else if(10<=x<25)
               ^
/in/foo.c:11:12: warning: comparisons like 'X<=Y<=Z' do not have their mathematical meaning [-Wparentheses]
  else if(10<=x<25)
          ~~^~~
/in/foo.c:13:2: error: expected expression before 'else'
  else if(x>=25)
  ^~~~