How to get past the final barriers in “The Real World”

I remember this game, it's awesome. I don't remember the code, but the internet does (as well as how to figure it out):

THE SECURITY DOOR: First use an infra red scan on the keypad. This will display a reading of heat from the previous person to access the door. The keys are cooling off in the order in which they were touched, allowing you to read the combination, which is 2571. After punching in the code, press the enter key on the keypad to open the door.

There's another part where you need a code to close a door, and you get that from a computer somewhere else:

THE ELEVATOR PUZZLE: You must have a code to close the elevator doors to prevent being killed by the blast grenade. The code is at the H. Suzuki computer terminal. You will find dossiers for the people who work in the complex. A temporary access code has been given to a new employee who is the last record in the terminal. Obtain the code and return to the elevator. Enter the code quickly to avoid being killed by the grenade. To enter the code correctly, you must repeatedly press the buttons to cycle through the available choices.

The Halon system was a gas chamber:

GUARD BEHIND GLASS WALL: You will find yourself in a storeroom on the lower level of the complex with a guard behind a glass wall. If he sees you he will activate a Halon System and flood the room with poisonous gas. You must sneak past this guard. Watch his cycling movements from the computer terminal to his notes. Sneak past him when he turns away from the window. Once past him, take the door out into the corridor. The first door on the left is the room he is working in. Enter the room and kill him.

Speaking from my coding experience; If I am understanding this correctly, your pointers point to memory addresses where certain values reside which you want to modify. A pointer is just a variable that instead of saving some value, saves a memory location.

You need find the addresses again for every time you restart the game. The reason for this is that the Operating System keeps track of allocated memory and which processes that have allocated that memory. Each process maintains its separate memory space. Memory is not an infinite resource so when a process exits, is shut down or killed, the memory tied to that process is released and becomes available for other processes to use. When a process needs a certain amount of memory, the operating system attempts to allocate that memory somewhere in the memory where there is enough space and then gives the process a link to that memory. However, depending on the current state of system memory and all the other things that are in it, you can never really be sure where that memory might be found. This causes the addresses to be different for each run.

Here's a link to Memory Addresses at Wikipedia and there are plenty of other resources on how computer memory work available online.