AKMA’s Random Thoughts

The Disseminary blog needs active links to the new cards -- I located them by substituting the logical filename. ;)

Our next line looks familiar, except it starts with an asterisk. Again, we're using the star operator, and noting that this variable we're working with is a pointer. If we didn't, the computer would try to put the results of the right hand side of this statement (which evaluates to 6) into the pointer, overriding the value we need in the pointer, which is an address. This way, the computer knows to put the data not in the pointer, but into the place the pointer points to, which is in the Heap. So after this line, our int is living happily in the Heap, storing a value of 6, and our pointer tells us where that data is living.

This will allow us to use a few functions we didn't have access to before. These lines are still a mystery for now, but we'll explain them soon. Now we'll start working within the main function, where favoriteNumber is declared and used. The first thing we need to do is change how we declare the variable. Instead of

This is another function provided for dealing with the heap. After you've created some space in the Heap, it's yours until you let go of it. When your program is done using it, you have to explicitly tell the computer that you don't need it anymore or the computer will save it for your future use (or until your program quits, when it knows you won't be needing the memory anymore). The call to simply tells the computer that you had this space, but you're done and the memory can be freed for use by something else later on.

The Stack is just what it sounds like: a tower of things that starts at the bottom and builds upward as it goes. In our case, the things in the stack are called "Stack Frames" or just "frames". We start with one stack frame at the very bottom, and we build up from there.

Our next line looks familiar, except it starts with an asterisk. Again, we're using the star operator, and noting that this variable we're working with is a pointer. If we didn't, the computer would try to put the results of the right hand side of this statement (which evaluates to 6) into the pointer, overriding the value we need in the pointer, which is an address. This way, the computer knows to put the data not in the pointer, but into the place the pointer points to, which is in the Heap. So after this line, our int is living happily in the Heap, storing a value of 6, and our pointer tells us where that data is living.

Inside each stack frame is a slew of useful information. It tells the computer what code is currently executing, where to go next, where to go in the case a return statement is found, and a whole lot of other things that are incredible useful to the computer, but not very useful to you most of the time. One of the things that is useful to you is the part of the frame that keeps track of all the variables you're using. So the first place for a variable to live is on the Stack. This is a very nice place to live, in that all the creation and destruction of space is handled for you as Stack Frames are created and destroyed. You seldom have to worry about making space for the variables on the stack. The only problem is that the variables here only live as long as the stack frame does, which is to say the length of the function those variables are declared in. This is often a fine situation, but when you need to store information for longer than a single function, you are instantly out of luck.