[讨论]关于一个制造钻石型东西的问题

#include<stdio.h>
main()
{
int num;

while (num != 0){
if (num == 0)
return 0;
printf("Enter a number (3-77):\t");
scanf("%ld", &num);
while (num>77 || num<3){
printf("Enter error!\n");
printf("Please enter a number(3-77):");
scanf("%d", &num);
}
for (int i=0; i<=(num-1)/2; i++)
{
for (int k=0; k<=num/2-i; k++)
printf(" ");
for (int j=0; j<=2*i; j++)
printf("*");
printf("\n");
}
for (int w=0; w<=num/2; w++){
for (int m=-1; m<=w; m++)
printf(" ");
for (int n=1; n<=(num-2)-2*w; n++)
printf("*");
printf("\n");
}
}
}，请问里面i<=(num-1)/2，k<=num/2-i,k<=num/2-i,w<=num/2,m<=w分别代表什么？？？因为我把数字改了以后有不同结果，还有printf(" ");有什么作用，因为删除了整个图形就变了

----------------解决方案--------------------------------------------------------
改了之后的代码，运行结果如图
#include<stdio.h>
main()
{
int num,i,k,j,w,m,n;
scanf("%ld", &num);
while (num != 0){
if (num == 0)
return 0;
printf("Enter a number (3-77):\t");
scanf("%ld", &num);
while (num>77 || num<3){
printf("Enter error!\n");
printf("Please enter a number(3-77):");
scanf("%d", &num);
}
for (i=0; i<=(num-1)/2; i++)
{
for (k=0; k<=num/2-i; k++)
printf(" ");
for (j=0; j<=2*i; j++)
printf("*");
printf("\n");
}
for (w=0; w<=num/2; w++){
for (m=-1; m<=w; m++)
printf(" ");
for (n=1; n<=(num-2)-2*w; n++)
printf("*");
printf("\n");
}
}
}

----------------解决方案--------------------------------------------------------