c语言入门bug求解

Question

求123*...*1000的乘积时出现了以下bug，求解！

#include <stdio.h>
int main()
{
int a=1,int b=2,int c;
for(;a<=999;a=c,b++)
{
c=a*b;
}
printf("%d",c);
return 0;
}

错误描述
expected gcc [行4,列14]
'c' undeclared (first use in this function) gcc [行5,列19]
'b' undeclared (first use in this function) gcc [行5,列21]
left-hand operand of comma expression has no effect [-Wunused-value] gcc [行5,列20]

Answer 1

#include <stdio.h>
int main()
{
int a=1,b=2,c;
for(;a<=999;a=c,b++)
{
c=a*b;
}
printf("%d",c);
return 0;
}