hello i m a beginer at c language

i have a gcc compiler on suse linux 9.3
 i tried to compile following code and it did sucessfully
main()
{
int a;
scanf("%d",&a);
int num[a];
...
...
}

while i beleive that there are 2 problems
1. all initializations should be the first thing to do.
2. array declarations should only be static.

i confirmed that i do not have a c++ compiler.
please help me out.