编译器的问题？ vb6.0 VS visual studio 2012

程序代码：#include

void main()

{

int i=3,j=5;

int *p,*q;

p=&i;

q=&j;

float a=5.8,b=7.9;

float *c,*d;

c=&a;

d=&b;

char m='I',n='L';

char *x,*y;

x=&m;

y=&n;

printf("i=%d, j=%d\n",*p,*q);

printf("a=%g, b=%g\n",*c,*d);

printf("m=%c, n=%c\n",*x,*y);

}

以上很简单的一段代码，主要是试试用指针，在vb6.0里面可以实现，但是在ms visual studio 2012里面，就不行

编译不通过

1>------ Build started: Project: Have a try, Configuration: Debug Win32 ------

1>  Have a try.c

1>c:\users\dell\documents\visual studio 2012\projects\have a try\have a try\have a try.c(9): error C2143: syntax error : missing ';' before 'type'

1>c:\users\dell\documents\visual studio 2012\projects\have a try\have a try\have a try.c(10): error C2143: syntax error : missing ';' before 'type'

1>c:\users\dell\documents\visual studio 2012\projects\have a try\have a try\have a try.c(11): error C2065: 'c' : undeclared identifier

1>c:\users\dell\documents\visual studio 2012\projects\have a try\have a try\have a try.c(11): error C2065: 'a' : undeclared identifier

1>c:\users\dell\documents\visual studio 2012\projects\have a try\have a try\have a try.c(11): warning C4047: '=' : 'int' differs in levels of indirection from 'int *'

1>c:\users\dell\documents\visual studio 2012\projects\have a try\have a try\have a try.c(12): error C2065: 'd' : undeclared identifier

1>c:\users\dell\documents\visual studio 2012\projects\have a try\have a try\have a try.c(12): error C2065: 'b' : undeclared identifier

1>c:\users\dell\documents\visual studio 2012\projects\have a try\have a try\have a try.c(12): warning C4047: '=' : 'int' differs in levels of indirection from 'int *'

1>c:\users\dell\documents\visual studio 2012\projects\have a try\have a try\have a try.c(14): error C2143: syntax error : missing ';' before 'type'

1>c:\users\dell\documents\visual studio 2012\projects\have a try\have a try\have a try.c(15): error C2143: syntax error : missing ';' before 'type'

1>c:\users\dell\documents\visual studio 2012\projects\have a try\have a try\have a try.c(16): error C2065: 'x' : undeclared identifier

1>c:\users\dell\documents\visual studio 2012\projects\have a try\have a try\have a try.c(16): error C2065: 'm' : undeclared identifier

1>c:\users\dell\documents\visual studio 2012\projects\have a try\have a try\have a try.c(16): warning C4047: '=' : 'int' differs in levels of indirection from 'int *'

1>c:\users\dell\documents\visual studio 2012\projects\have a try\have a try\have a try.c(17): error C2065: 'y' : undeclared identifier

1>c:\users\dell\documents\visual studio 2012\projects\have a try\have a try\have a try.c(17): error C2065: 'n' : undeclared identifier

1>c:\users\dell\documents\visual studio 2012\projects\have a try\have a try\have a try.c(17): warning C4047: '=' : 'int' differs in levels of indirection from 'int *'

1>c:\users\dell\documents\visual studio 2012\projects\have a try\have a try\have a try.c(20): error C2065: 'c' : undeclared identifier

1>c:\users\dell\documents\visual studio 2012\projects\have a try\have a try\have a try.c(20): error C2100: illegal indirection

1>c:\users\dell\documents\visual studio 2012\projects\have a try\have a try\have a try.c(20): error C2065: 'd' : undeclared identifier

1>c:\users\dell\documents\visual studio 2012\projects\have a try\have a try\have a try.c(21): error C2065: 'x' : undeclared identifier

1>c:\users\dell\documents\visual studio 2012\projects\have a try\have a try\have a try.c(21): error C2100: illegal indirection

1>c:\users\dell\documents\visual studio 2012\projects\have a try\have a try\have a try.c(21): error C2065: 'y' : undeclared identifier

========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

请问大家，这是为什么呀？

如果将程序代码改成

程序代码：#include

void main()

{

int i=3,j=5;

int *p,*q;

float a=5.8,b=7.9;

float *c,*d;

char m='I',n='L';

char *x,*y;

p=&i;

q=&j;

c=&a;

d=&b;

x=&m;

y=&n;

printf("i=%d, j=%d\n",*p,*q);

printf("a=%g, b=%g\n",*c,*d);

printf("m=%c, n=%c\n",*x,*y);

}

就 OK了，这又是为什么呀？

谢谢