在C语言中，合法和非法的声明和初始化

Datatype v1,v2,… vn;

float a,b;

int a, b; /* global declaration*/
main ( ){
   int c; /* local declaration*/
   - - -
}

Datatype v1=number;

int sum=0;
float a=1,b=4.5;

#include
void main ( ){
   int a,b;
   a= 10, b = 20;
   printf (" %d", ab);
   printf (" %d", a>=b);
   printf (" %d", a = =b);
   printf (" %d", a ! =b);
}

1 1 0 0 0 1

#include 
int main(){
   static int p=20, q=p*p;//illegal initialization
   printf("%d%d",p,q);
   return 0;
}

error will be occurred
error: initializer element is not constant
   static int p=20, q=p*p;