Essentials: Hidden Pointers - Computerphile

Pointers are an essential element of computing. Dr Steve Bagley explains how everything rests on pointers.

Many thanks to Microsoft Research UK for their support with the 'Essentials' mini-series.

This video was filmed and edited by Sean Riley.

[beachhouse]

Oh WOW! I checked out "The 8088 Project Book" from my library back in 1996. I really enjoyed reading it and took it with me wherever I went for those 2 weeks as I just couldn't get enough. Sadly, after I returned it, I couldn't remember the name thus I could never find it again to check back out. Even now, 21 year later, I still think about that book from time to time. The moment Dr. Bagley showed the cover, I almost fell out of my chair. That picture has been ingrained in my memory. A few more moments of watching and some quick research showed that it was indeed the long lost book from my past. So thank you Dr. Bagley and Computerphile, thank you, thank you, thank you! Now off to amazon.... Well, I should probably watch the rest of the video first.

[custersword]

Beautifully simple explanation of such an important part of computers. Thank you.

[eronin]

i could listen to dr.bagley pointing out things all day long :)

[silakanveli]

Wonderful video. Finally someone gives underlying reason for pointers. Please do part 2

[ylluminarious]

Great explanation of why low-level programming is still essential to know of and understand. It's not at all "obsolete." Also, that book you have reminds me of another book I have about programming on the 8088... it's called "IBM PC & XT Assembly Language: A Guide for Programmers", by Leo J. Scanlon. It's very educational and well-written. Recommend it to anyone who is curious about assembly or who wants to cut their teeth on low-level stuff.

[Nick-kbjc]

You don't get the point of pointers until you use pointers and then you get the point.

[jeffirwin]

I can't understand this without a lego analogy.

[anon]

You can't build a computer with a Von-Neumann architecture without pointers, but what about other kinds of computer architectures?

[psychogat]

does the max size of the pointer limit the amount of memory that can be used? is that why some laptops can only have like 4 or 8gb of ram?

[huldu]

I could never understand what a "pointer" was back in school. The teacher was so awful, the kind that is only there for the pay and doesn't give a damn about anything else. Good times.

[PvblivsAelivs]

I suppose that's a different way of thinking about it. But "pointer" was a term created to name a feature in a high-level language. But at the machine level, it's just memory addresses. Sure, you need memory addresses. And memory addresses are how pointers are implemented. But this still looks like a way to shoehorn the term in.

[ElagabalusRex]

Who do almost all languages since C completely hide pointer arithmetic? What would be the ramifications of adding optional support pointer types to Java and Python?

[lierdakil]

... I don't get the rant at the end. Surely as long you have addressable memory, processor will use memory addresses, that's a given. But addressable memory is implementation detail. Why we "can't have" abstract algorithms if we don't have memory addresses is a mystery. I can run lambda calculus in my head, for example, and I'm pretty sure I don't need to think about pointers to do that.

[rosieisla]

I CANNOT be the only person who went at least a minute trying to figure out how this related to computer mice.

[alexanderwikstrom]

Mind if I just point out that the definition of a pointer is: "A value that is stored in memory that contains the memory address of another memory location."
And that the term memory in computing science is most often only extending to the main memory in a system, in other words Main RAM, and not to Hard drives, SSDs or Registers.
Therefor stating that the program counter (that is a register) is a pointer is a bit wrong. And yes, some call it an instruction pointer, but that can get into confusion with a register that references the current instruction span for the instruction decoder. (A lose form of compression used in a few CISC architectures.)

[ze_rubenator]

I suddenly learned where the droid 8t88 from Jedi Knight: Dark Forces II got his name.

[Noddy]

can I get some recommendations of websites or modern books that describe the theme and concepts of this video?

[IllidanS]

At the basis, indirection is necessary. Whether in the form of a pointer or something else, that's another debate.

[banderi]

"Think of it like the index of a book" *opens up the glossary*

[DrGreenGiant]

Could you explain how the CPU knows whether what is stored at an address is a pointer or a value, i.e. how does it know what the type is (coming from a C background)