Gadgetory

hello there my name's Gary Sims from Android Authority now if you hang around with nerds with technical people long enough maybe they'll use vocabulary that you're not familiar with they might use words like machine code or assembly language when they use it you kind of just smile sweetly and let the conversation carry on because you don't really know what they're talking about well today I want to explain to you what is machine code on what is assembly language now we're all used to running multiple programs on our mobile devices whether they're laptops tablets or smartphones we ran a program we started up we use it we closed it we start another one where there's a word processing suite an email client a game a graphics program we're very used to going into a program exiting it and then going into another one but it wasn't always like that at the beginning of the history of computing the initial computers were hardwired they could only perform one task the circuit that was built into them that was the task that they performed of course it became obvious very quickly that we need a universal computer one that can perform any task so it's programmed to do now there are two key characters in the history of the development of these stored-program one is Alan Turing and the other is John von Neumann now Alan Turing is famous for breaking the Enigma code during the Second World War but he also did a lot of other things related to computer science and particularly he came up the idea of a thing called the Turing machine now he proved with the Turing machine you could execute any computable algorithm I were boy the details of how he talked about it but basically had the idea of some symbols that could be read and other symbols could be written to a tape because that was the technology of the time now this idea was picked up and taken further by John von Neumann and von Neumann proposed the idea of a CPU a central processing unit with some memory random access memory and that the CPU executed instructions and then could alter the random access memory in fact the majority of computers that we use today use what we call the von Neumann architecture what does all this have to do with machine code and assembly language well machine code is the name given for those instructions are executed by the central processing unit they're bad in fact just numbers they're a long number that tells the to do something for example under the ARM architecture the number 288 means move one inter-village to zero now a CPU has registers that kind little pots little holes you can put data in and you can do something with them quickly and then maybe put something else in there very temporary even the arm 64 chips for example only have 64 registers so they can't replace main memory not talking about gigabytes he'd you're talking about a few places to store temporary data man they're great when you want to perform maybe do something the string you can do things in little registers now each of these numbers 288 move one into register 0 each of these numbers mean something different now of course if you imagine writing that by hand trying to remember what 288 is what is 329 though what is 54 do all these different numbers would be almost impossible so in fact there's another thing which is a slightly higher level more human-friendly version of machine code called assembly language and rather than just talking with raw numbers there's some opt codes some short codes that say I want to move something into a register that here's an example as you can see that tells us we want to move one into register 0 now assembly language when you start writing it it's in a text file it has to be converted into the machine code by a thing called an assembler so an assembler takes this very low-level code and turned it into machine code which the CPU knows how to execute so here's another snippet of assembly language so you can kind of get an idea of what it looks like now what this one does is it takes the number 15 and puts it into register 3 and then stores it somewhere on the stack now I'm not gonna getting to stack now but base is a part of memory and it says here that this number is stored 8 bytes down the stack it then takes a number 25 and sticks it into r3 and then says let's store that at the 12th position on the stack and then finally it adds those two numbers together and store the result again in r3 now in a higher-level language like C or Java you would probably do this in just three lines I is equal to 15 J is equal to 25 I is equal to I plus J so as you can see using a higher-level language is easier to three lines of code rather than eight now imagine if you had to write a game like clash Royale or Riptide GP using just assembly language now it would be possible and in fact in the days of the home micro revolution the BBC micro is a tech spectrum the Commodore 64 that's what game programmers did they wrote it all in assembly language quite an amazing feat if you think about it but today we would use a compiled in our compiler takes a high-level language like C and converts it directly into the machine code so the C compiler looks at what you want to do normal to set this variable I want to add these two numbers and it works out what it needs to do in the assembly language and then in the machine code to actually get that to happen now there are other programming languages in Java for example which is the main programming language for Android apps what actually happens you use a compiler that converts the Java code into Java byte code kind of like a type of machine code bits for a virtual machine not for a real physical processor but for one a virtual one that exists on the Android phone it runs through a thing called a virtual machine which interprets those byte codes those machine instructions and turns them into real instructions for the ARM processor or for an Intel processor or for a mixed process and the idea of course is that therefore you can write apps and you can actually have them on any architecture that you want because it's the virtual machine that running them and then there's one little step you have to write when you implement Android to make it work on that particular processor cause at the moment the ARM processor is the most dominant one so you've got a compiler that converts it into a bytecode and a virtual machine that runs it on the Android phone now if you want real high performance then you really should be writing your game let's say or your mathematical modeling program or whatever is you want to do in C or even in assembler language and that's possible there's a thing called in native development kit the NDK which you can get from Google it allows you to write C and assembly language directly on your Android phone and that bypasses that a virtual machine and using compilers and assemblers to create that code but let me warn you nerds only need apply so let's do a quick sum up here so that you can really get the essence of what's going on here old days computers fixed didn't have to couldn't do multiple tasks weren't universal go do one thing invented the idea cheering and von Neumann ad the idea of universal computers that could have memory and a CPU and they can execute instructions and those instructions are called machine code for us humans to create that machine code there's a slightly higher level a readable form called assembly language which converts directly into machine code and then above that you get languages like C and Java and other languages that exist that can compile to machine code to run on a processor I hope you got all that my name's Gary sim from Andrew authority and I hope you enjoyed this video if you did please do give it a thumbs up also please use the comments below to tell me whether you've written any machine code have you written any assembly language do you like writing in high-level languages do tell us about your experiences with these low-level things on your Android phone also don't forget to subscribe to and royalties YouTube channel you can follow me on Twitter and if you use this link here you can find me on the and Roth or 'ti forums there's a place on the forums where you can ask me any question ask me that machine code ask me about assembler and if I can help you I'll get back to you and also don't forget to stay tuned to an authority comm because we are your source for all things Android