Assemble several interesting experiments

Lab 1:

Enter the following command, I first use the a command to enter, and with the T command for single-step debugging.

It can be found that the AX,BX has changed under different commands, and the IP value is constantly increasing depending on the length of the input instruction. Later I used the G command to perform a single execution (the result is the same as one step).

It is important to note that the final range of G should be the address at the end of the command, not the next address.

Then I tried using the e command.

First disassembly looked down and found no problem.

However, when I try to use the G command to complete a one-time execution is a problem, when I executed to the second-to-last address is a success, and execution to the final address but there is a state of death, I tried to use different methods have failed, do not know why, help the big guy.

Lab 2:

Use 3 instructions to complete 2 of the 8-square calculation. Here I'm using the 7-time JMP command to complete the calculation. Remember to change the initial value of CS and IP as we wrote from 2000:0, not from the default address.

Then use T to start the single-step debugging, because the first to perform 2 moves and additions, the following jmp each time to execute 2 times, a total of 7 times in jmp, so the total to execute the T command 16 times to get the desired results.

Here you can see that the 16 binary of AX is converted to 0100 to 10, which is 2 of the 8 square 16.

Lab 3:

Here to find the production date in FFF00H~FFFFFH. So I used the D command to start looking up from fff0:0 and found an interesting phenomenon.

With these graphs, you can see that in each segment the address from fff0 to FFFF appears in the 00x0 01/01/92 this value (x is 0~f) and the last of the segment address has such a relationship with the X in 00x0 the last one is defined as Y (that is, Fffy) y+x=16 The address of the 00x0 will appear 01/01/92. Then I tried to modify the value, and found that it was not possible to modify the success.

Lab 4:

Try to modify the values in a contiguous b8100 of memory, and the situation arises.

And then I change it somewhere else and that doesn't happen.

Later, the book found that the memory cell address from the A0000~BFFFF are video memory addresses, there will be some patterns.

Summarize:

After these experiments, we have a preliminary understanding of some of the instructions in the compilation, and also realized the convenience of the compilation to the memory modification. Here are a few more questions.

1. Experiment 1: However, when I try to use the G command to complete a one-time execution is a problem, when I executed to the second-to-last address is successful, and the execution to the final address but there is a state of death, I tried to use a different method failed, do not know why, help the big guy.

2. Experiment 2: There is a problem here, because JMP will execute indefinitely, so how can you abort the program.

3. Experiment 3: There is also a question, if this is the date of production, why the number of/92. As we all know, one months at most only 31 days. Did I get the wrong one or what?

Assemble several interesting experiments