WEBVTT 1 00:01.730 --> 00:03.230 Hello and welcome back. 2 00:03.230 --> 00:10.580 In this lesson, we are going to learn about INC and DEC. INC is to increment, and DEC is to decrement. 3 00:10.730 --> 00:13.820 So there are basically these two forms. 4 00:13.820 --> 00:17.780 We have the INC register and INC memory. 5 00:18.020 --> 00:20.870 We also have the DEC register and DEC memory. 6 00:21.080 --> 00:25.160 So INC will increase the whatever value in register by one. 7 00:25.370 --> 00:30.020 And it also increases whatever value is in the memory by one. 8 00:30.350 --> 00:36.200 DEC will have the opposite effect. That will decrease whatever in the register by one. 9 00:36.440 --> 00:39.500 It will also decrease whatever in the memory by one. 10 00:39.500 --> 00:43.730 So let's open up our x64dbg now and try this. 11 00:44.480 --> 00:47.690 So we put a breakpoint, and we run to our breakpoint. 12 00:48.020 --> 00:50.450 Then we step over until we come to this line. 13 00:50.450 --> 00:54.680 Now we will put a value in the register of 10. 14 00:55.250 --> 01:01.790 So we right-click in our -, modify, and put one over there. Click okay. 15 01:03.570 --> 01:05.760 So now we have 1 in -. 16 01:06.780 --> 01:10.140 So now we are going to increment our -. 17 01:10.980 --> 01:16.590 So let's enter the instruction INC -. 18 01:19.430 --> 01:24.320 Then we step over that, and now our - becomes two. 19 01:25.400 --> 01:27.860 Now we'll try a memory. 20 01:28.370 --> 01:31.640 So let's select Dump 1 as a default. 21 01:32.180 --> 01:33.440 Click on memory map. 22 01:33.680 --> 01:39.410 Go to the BSS segment for variables, and then double-click on it. 23 01:40.640 --> 01:42.290 And then at the bottom, Dump 1. 24 01:42.290 --> 01:42.950 Scroll down. 25 01:42.950 --> 01:44.990 Look for blank empty space. 26 01:45.590 --> 01:46.850 This one, maybe. 27 01:47.030 --> 01:53.870 And then right-click and put a value there. Binary edit. 28 01:54.020 --> 01:58.010 And let's put 03 03. 29 01:58.700 --> 01:59.540 Click okay. 30 02:00.290 --> 02:02.060 And then we have three there now. 31 02:02.870 --> 02:04.160 Right-click this address. 32 02:06.600 --> 02:07.980 Copy address. 33 02:08.070 --> 02:14.730 So now we are going to INC the memory location, this memory location, and see what happens to three. 34 02:15.240 --> 02:21.150 So let's assemble an instruction for INC. Type INC keyword. 35 02:22.790 --> 02:28.250 BYTE PTR, and then put your memory there. 36 02:30.810 --> 02:31.560 Then you have copied. 37 02:32.130 --> 02:33.180 Click okay. 38 02:34.740 --> 02:38.340 So now we are going to execute this and watch what happens here. 39 02:40.350 --> 02:47.280 And you will see that the value in this location of memory has been incremented by one. 40 02:47.340 --> 02:48.900 So now it becomes four. 41 02:48.900 --> 02:50.250 Previously it was three. 42 02:51.060 --> 02:55.320 Now we'll take a look at the reverse of INC. We will study DEC. 43 02:56.010 --> 02:59.430 So now we are going to do the reverse of what we did for -. 44 02:59.460 --> 03:01.380 We are going to decrement our -. 45 03:01.380 --> 03:02.580 So let's do that now. 46 03:04.290 --> 03:06.720 Assemble DEC -. 47 03:09.700 --> 03:15.880 Click okay, and let's execute this instruction and watch our -. 48 03:16.030 --> 03:22.540 Currently it's two. Step over, and our - becomes one. 49 03:23.140 --> 03:25.660 So it has decremented it by one. 50 03:26.260 --> 03:28.810 Now we'll try decrement memory. 51 03:28.930 --> 03:31.570 So again, we copy this memory here. 52 03:34.850 --> 03:40.190 Then we go to this line and assemble a decrement for that memory. 53 03:42.480 --> 03:44.850 BYTE PTR. 54 03:48.030 --> 03:57.060 And then okay. Now we are going to execute this line and see what happens to the value in this memory. 55 03:59.260 --> 04:02.440 It has decreased by one, and now it becomes three. 56 04:02.740 --> 04:08.620 So this is how you can use the INC and DEC instructions in your x64dbg. 57 04:09.460 --> 04:10.840 That's all for this video. 58 04:10.840 --> 04:12.250 Thank you for watching.