Q:

Seeing if an infinite loop in C++ will occur

Will the following code result in infinite loop? 
  x=0;
  y=0;

  while(x<100)
  {
    minnum=100;
    maxnum=100;
    while(y<150)
    {
    if(random[x][y]<minnum)
      {
      minnum=random[x][y];
      minX=x;
      minY=y;
      y++;
      }
    else if(random[x][y]>maxnum)
      {
      maxnum=random[x][y];
      maxX=y;
      maxY=y;
      y++;
      }
    }
    x++;
    y=0;
  }  

A:

If both random[x][y]<minnum and random[x][y]>maxnum are false, you'll never exit out of the inner loop.  More specifically if random[x][y] == 100 you're toast the first time through. 
As a related question, what behavior do you see when you debug the source you've posted?