WEBVTT 00:01.470 --> 00:06.240 In this video, let's discuss some most commonly used stack instructions. 00:06.810 --> 00:08.900 Let's begin by writing a simple program. 00:09.150 --> 00:14.040 I'm going to create a new file called Push, Flash, Pop, not Nazim. 00:20.860 --> 00:29.350 And as usual, I'm going to start with a global directive, so let's type global space and let's start 00:29.920 --> 00:37.740 and let's specify this start as our entry point here and let's first write the instruction, move our 00:37.750 --> 00:39.250 eggs, comma 20. 00:41.320 --> 00:48.640 Next, let's push the value stored in this register under the stack by using the instruction push at 00:48.660 --> 00:49.150 X. 00:49.850 --> 00:55.910 So I'm typing push out X, let's push the value stored in the register under the stack. 00:55.930 --> 01:03.700 Once again I'm typing push out X and then let's use pop idea. 01:04.330 --> 01:10.450 What this instruction will do is whatever the value that we have recently pushed onto the stack will 01:10.450 --> 01:12.730 be popped into the idea register. 01:13.450 --> 01:17.140 Now let's also type pop RB X. 01:17.800 --> 01:21.880 This time the value on the top of the stack will be popped into the register. 01:21.880 --> 01:22.690 RB X. 01:23.350 --> 01:30.160 Now let's save the file and let's once again assemble and link it. 01:31.570 --> 01:48.070 Nazem pushpa dot nazeem dash o push pop dot o f l sixty four and let's say early push pop dot o bargepole 01:48.760 --> 01:50.200 push nasch pop. 01:50.950 --> 01:52.920 So that's going to be our output file. 01:54.760 --> 01:56.830 Now let's open it up using GDP. 01:57.190 --> 02:10.660 I'm typing gdb dot slash, push, dash, pop and let's set up an entry point at underscore start and 02:11.290 --> 02:12.040 let's run it. 02:14.500 --> 02:15.120 Here we are. 02:15.160 --> 02:19.840 This is the disassembly and observe what we have on the top of the stack. 02:19.840 --> 02:24.430 At this point of time we have value one on the top of the stack. 02:24.850 --> 02:29.590 Now let's type say to move the value hex falling into X. 02:30.100 --> 02:31.390 I'm typing s.A. 02:36.290 --> 02:45.830 As you can see here, the register adex contains the value hex 14 now still the top of the stack contains 02:45.830 --> 02:46.610 value one. 02:47.000 --> 02:52.680 And we are about to push the value that is stored in order to register onto the stack. 02:53.060 --> 03:00.800 So once this instruction gets executed, the value that is currently stored in our eggs will be pushed 03:00.950 --> 03:01.850 onto the stack. 03:02.240 --> 03:03.590 So let's take a say. 03:05.090 --> 03:10.700 And as you can see now, the top of the stack is pointing to the value hex 14. 03:11.300 --> 03:16.040 Now, the next instruction to be executed is one more push IREX. 03:16.490 --> 03:20.710 That means we should see another similar entry on the stack now. 03:21.050 --> 03:25.730 So let's step aside a look at that push. 03:25.730 --> 03:31.220 IREX instruction has pushed the value HEX 14 onto the stack once again. 03:31.790 --> 03:36.080 Now the next instruction to be executed is pop idea. 03:36.860 --> 03:40.750 Pop is one instruction that people always get confused about. 03:41.030 --> 03:43.040 So try to put some attention here. 03:43.430 --> 03:51.530 When you execute pop space aspecific register, what happens is whatever the value that we have on the 03:51.530 --> 03:55.560 top of the stack is going to be popped into the register. 03:56.150 --> 04:02.780 In this case, the register idea is going to contain the value hex 14 because that's the value that 04:02.780 --> 04:04.070 is on the top of the stack. 04:04.880 --> 04:08.540 So let's execute this idea before executing that. 04:08.730 --> 04:12.600 Let's quickly check the value that we currently have in our day register. 04:13.130 --> 04:14.950 If you notice, it's zero. 04:15.560 --> 04:22.260 So after executing this instruction, we should see the value hex 14 in the register idei. 04:22.700 --> 04:24.020 So let's say. 04:26.310 --> 04:33.990 And check the value of our register, if you look at this, the register ardia contains Heggs 14 this 04:33.990 --> 04:34.260 time. 04:34.890 --> 04:37.660 So that's how pop instruction works. 04:38.150 --> 04:39.170 Now, look at that. 04:39.210 --> 04:41.720 We have another pop instruction now. 04:41.730 --> 04:47.680 This time the value on the top of the stack is going to be popped into our vic's register. 04:48.090 --> 04:53.170 So let's step aside and check what happened to the RBA register before that. 04:53.280 --> 04:57.210 Once again, let's quickly check the current value of RB X register. 04:57.660 --> 04:59.210 It's currently zero. 04:59.730 --> 05:01.140 So let's take aside. 05:03.140 --> 05:11.030 And once again, let's go back and check our bags and look at that, the value X 14 is popped into our 05:11.030 --> 05:11.900 vehicles registered. 05:12.590 --> 05:15.680 This is how push and pop instructions. 05:15.680 --> 05:16.130 What?