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These are the user uploaded subtitles that are being translated: 1 00:00:00.05 --> 00:00:02.06 - [Instructor] Computers of all shapes and sizes 2 00:00:02.06 --> 00:00:04.04 achieve their computational tasks 3 00:00:04.04 --> 00:00:07.07 by manipulating binary data, zeros and ones, 4 00:00:07.07 --> 00:00:09.00 using a set of instructions, 5 00:00:09.00 --> 00:00:12.04 built into the hardware of their chip sets. 6 00:00:12.04 --> 00:00:13.09 These instructions themselves 7 00:00:13.09 --> 00:00:16.01 are represented as zeros and ones 8 00:00:16.01 --> 00:00:18.05 in what's known as machine code. 9 00:00:18.05 --> 00:00:20.08 For as humans it's a bit mind numbing 10 00:00:20.08 --> 00:00:23.02 looking at just zeros and ones. 11 00:00:23.02 --> 00:00:25.04 So we aggregate them into sets of four bits 12 00:00:25.04 --> 00:00:27.02 and call them hexadecimal. 13 00:00:27.02 --> 00:00:29.06 Represented by the numbers no to nine, 14 00:00:29.06 --> 00:00:34.07 and the letters A to F 16 possible values in total. 15 00:00:34.07 --> 00:00:36.06 Chip manufacturers will have their own set 16 00:00:36.06 --> 00:00:39.04 of instructions for their chips. 17 00:00:39.04 --> 00:00:41.02 The most popular instruction set 18 00:00:41.02 --> 00:00:44.05 is that used with the Intel x86 chip. 19 00:00:44.05 --> 00:00:47.06 Two of the commonly seen chip sets are they ARM chip 20 00:00:47.06 --> 00:00:50.01 which is the most popular mobile phone chip, 21 00:00:50.01 --> 00:00:51.05 and the Atmel chip, 22 00:00:51.05 --> 00:00:55.01 which appears in many small IoT type devices. 23 00:00:55.01 --> 00:00:56.03 For the purposes of this course, 24 00:00:56.03 --> 00:00:59.08 we'll be focusing on the x86 chip set. 25 00:00:59.08 --> 00:01:01.07 Instructions are executed in what's known as 26 00:01:01.07 --> 00:01:03.07 the central processing unit of the chip 27 00:01:03.07 --> 00:01:06.01 using a set of registers. 28 00:01:06.01 --> 00:01:07.04 Special areas of the chip, 29 00:01:07.04 --> 00:01:10.01 which are able to manipulate bits. 30 00:01:10.01 --> 00:01:12.01 We'll look at what these registers are shortly 31 00:01:12.01 --> 00:01:14.04 but as an example, the instruction 32 00:01:14.04 --> 00:01:17.09 to add 28 to a register called ESP 33 00:01:17.09 --> 00:01:22.09 will be coded in machine language as 83 C4 1C. 34 00:01:22.09 --> 00:01:24.09 Even this is a bit tricky for us. 35 00:01:24.09 --> 00:01:26.04 Although many low level programs 36 00:01:26.04 --> 00:01:29.00 can write machine code directly. 37 00:01:29.00 --> 00:01:31.04 It's more common however, to use mnemonics 38 00:01:31.04 --> 00:01:34.05 to represent the various parts of the instruction. 39 00:01:34.05 --> 00:01:37.08 And this is what's known as assembly language. 40 00:01:37.08 --> 00:01:39.02 So we'd code this instruction 41 00:01:39.02 --> 00:01:43.09 in assembly language as ADD ESP, 1C. 42 00:01:43.09 --> 00:01:46.03 And then we'd use a program called an assembler 43 00:01:46.03 --> 00:01:49.04 to convert this mnemonic form back to machine code 44 00:01:49.04 --> 00:01:52.09 ready for the computer to execute it. 45 00:01:52.09 --> 00:01:55.05 The general model that we can keep in the back of our minds 46 00:01:55.05 --> 00:01:59.06 as we program in assembler starts with the processing unit. 47 00:01:59.06 --> 00:02:01.00 This works most effectively 48 00:02:01.00 --> 00:02:03.06 with its set of high performance registers. 49 00:02:03.06 --> 00:02:05.02 However, we often need more 50 00:02:05.02 --> 00:02:08.00 than just what can be stored in registers. 51 00:02:08.00 --> 00:02:10.00 So we need to have a memory area 52 00:02:10.00 --> 00:02:12.04 which can be used to store our data 53 00:02:12.04 --> 00:02:14.06 and our program instructions. 54 00:02:14.06 --> 00:02:16.04 We want to interact with the program. 55 00:02:16.04 --> 00:02:18.08 So we need an input and output device 56 00:02:18.08 --> 00:02:21.03 usually a screen and keyboard. 57 00:02:21.03 --> 00:02:23.02 Of course, we also have other devices 58 00:02:23.02 --> 00:02:27.02 such as track pads and the mouse and then embedded products, 59 00:02:27.02 --> 00:02:29.08 we may display to an LED. 60 00:02:29.08 --> 00:02:33.04 However these are just variations on the general theme. 61 00:02:33.04 --> 00:02:35.03 While the internal memory of a computer 62 00:02:35.03 --> 00:02:38.07 gives us what we need to operate, we need more. 63 00:02:38.07 --> 00:02:40.03 While internal memory doesn't need to be 64 00:02:40.03 --> 00:02:42.01 as fast as registers. 65 00:02:42.01 --> 00:02:44.01 It needs to be fast enough. 66 00:02:44.01 --> 00:02:45.04 This means it's volatile. 67 00:02:45.04 --> 00:02:48.07 So its contents disappear when power is removed. 68 00:02:48.07 --> 00:02:51.02 Consequently, we need to also have access 69 00:02:51.02 --> 00:02:53.02 to backing storage of some sort. 70 00:02:53.02 --> 00:02:58.00 Typically a solid state or magnetic surface hard disk. 71 00:02:58.00 --> 00:03:00.09 The size of the instruction does matter. 72 00:03:00.09 --> 00:03:03.09 For X 86 much of the assembler code we see 73 00:03:03.09 --> 00:03:06.02 is written in 32 bit code. 74 00:03:06.02 --> 00:03:09.03 However with the advent of 64 bit processes 75 00:03:09.03 --> 00:03:11.05 more extensive instructions have been included 76 00:03:11.05 --> 00:03:15.00 in the 64 bit versions of the assembler tools. 77 00:03:15.00 --> 00:03:19.01 We'll cover both 32 and 64 bit instructions. 78 00:03:19.01 --> 00:03:23.00 Microsoft includes both 32 bit and 64 bit assemblers 79 00:03:23.00 --> 00:03:26.08 called ml.exe and ml64.exe 80 00:03:26.08 --> 00:03:29.03 in their software development kits. 81 00:03:29.03 --> 00:03:32.03 These tools can be accessed via visual studio 82 00:03:32.03 --> 00:03:35.01 by including them in a C ++ project 83 00:03:35.01 --> 00:03:37.09 or run directly in the command line. 84 00:03:37.09 --> 00:03:41.02 The MASM32 SDK is project developed 85 00:03:41.02 --> 00:03:43.09 around the Microsoft MASM32 product. 86 00:03:43.09 --> 00:03:46.04 Intended as a simpler and easier introduction 87 00:03:46.04 --> 00:03:50.06 to the Microsoft MASM32 bit programming environment. 88 00:03:50.06 --> 00:03:53.06 And it comes with a simple IDE. 89 00:03:53.06 --> 00:03:56.00 GoAsm is a very easy to use set of tools, 90 00:03:56.00 --> 00:03:58.00 providing assembly and linking 91 00:03:58.00 --> 00:04:01.04 of both 32 and 64 bits assembler programs. 92 00:04:01.04 --> 00:04:03.01 We'll be focusing on GoASM 93 00:04:03.01 --> 00:04:06.06 as our assembler of choice in this course. 94 00:04:06.06 --> 00:04:09.00 We've described a basic architecture 95 00:04:09.00 --> 00:04:12.07 with which we can process instructions that work on data. 96 00:04:12.07 --> 00:04:16.00 Let's look at the general classes of instructions. 97 00:04:16.00 --> 00:04:17.05 The first category of instructions 98 00:04:17.05 --> 00:04:19.02 is the load and store instructions, 99 00:04:19.02 --> 00:04:23.03 which move data between registers and memory locations. 100 00:04:23.03 --> 00:04:25.06 These include basic move and store instructions 101 00:04:25.06 --> 00:04:27.05 as well as some more esoteric instructions 102 00:04:27.05 --> 00:04:32.07 such as sign extensions and data exchange instructions. 103 00:04:32.07 --> 00:04:35.04 The second category is the set of instructions 104 00:04:35.04 --> 00:04:39.08 used to add, subtract, multiply, and divide. 105 00:04:39.08 --> 00:04:43.02 Which provide the computational capability of the chip. 106 00:04:43.02 --> 00:04:46.01 These include signed and unsigned operations 107 00:04:46.01 --> 00:04:50.01 Packed Decimal Format operations, floating point operations 108 00:04:50.01 --> 00:04:53.03 and increment and decrement operations. 109 00:04:53.03 --> 00:04:57.08 The third major category is bit wise or logical operations. 110 00:04:57.08 --> 00:05:00.04 These are special forms of manipulation at the bit level 111 00:05:00.04 --> 00:05:03.07 such as shifting, adding or calling and so on. 112 00:05:03.07 --> 00:05:06.01 And they are used for a variety of purposes 113 00:05:06.01 --> 00:05:08.08 including extracting parts of a memory location 114 00:05:08.08 --> 00:05:11.05 a process known as masking. 115 00:05:11.05 --> 00:05:13.09 The next category is that involving instructions 116 00:05:13.09 --> 00:05:17.04 which change the flow of execution of the program. 117 00:05:17.04 --> 00:05:20.05 The most basic form of coding is to perform an instruction 118 00:05:20.05 --> 00:05:23.00 move to the next sequential instruction location 119 00:05:23.00 --> 00:05:26.01 and perform that instruction and so on. 120 00:05:26.01 --> 00:05:28.08 However, we also need to make decisions 121 00:05:28.08 --> 00:05:31.02 on whether to move to the next instruction 122 00:05:31.02 --> 00:05:33.07 or to take an alternative path. 123 00:05:33.07 --> 00:05:35.05 We do this using a set of instructions 124 00:05:35.05 --> 00:05:37.08 which change the Control flow. 125 00:05:37.08 --> 00:05:40.02 This includes if statements, 126 00:05:40.02 --> 00:05:44.03 looping instructions and sub program calls. 127 00:05:44.03 --> 00:05:47.00 There's also a number of advanced capabilities of the chip 128 00:05:47.00 --> 00:05:50.01 including AES hardware capability. 129 00:05:50.01 --> 00:05:53.02 Packed decimal 128 bit instructions 130 00:05:53.02 --> 00:05:57.07 and 256 and larger vector instructions. 131 00:05:57.07 --> 00:06:00.09 We'll cover some of this advanced material in this course 132 00:06:00.09 --> 00:06:03.06 but after the course, you might want to check the full range 133 00:06:03.06 --> 00:06:06.07 of advanced instructions yourself. 134 00:06:06.07 --> 00:06:08.07 With that as an introduction 135 00:06:08.07 --> 00:06:11.06 let's get into learning how to write assembly code. 10983