max.c:2:13: error: parameter ‘a’ has just a forward declaration
 int max(int a;int b)
             ^
max.c: In function ‘max’:
max.c:4:8: error: ‘a’ undeclared (first use in this function)
     if(a>b){
        ^
max.c:4:8: note: each undeclared identifier is reported only once for each function it appears in