7.2 Copying a String

Write the following code `CopyStr.asm` using the text editor. Assemble and link the file.

Questions:
1. What are the values of the `si` register during the execution of loop L1?
2. What are the values of the `ecx` register during the execution of loop L1?
3. What is the meaning of the values of the `al` register during the execution of loop L1?
4. What is the value of the target string in memory before starting the execution of loop L1?
5. What is the value of the target string in memory after finishing the execution of loop L1?

7.3 Summing an Array of Integers

Program `SumArray.asm` uses register `si` as a pointer to `intarray`. Register-indirect addressing is used to access the elements of `intarray`. Write the following code:

1. What are the values of the `si` register during the execution of loop L1?
2. What are the values of the `ecx` register during the execution of loop L1?
3. What is the meaning of the values of the `al` register during the execution of loop L1?
4. What is the value of the sum (in decimal) at the end of the program?
5. How many iterations was loop L1 repeated?
6. Assuming the initial value of `si` is `404000h` before starting loop L1, what is the final value of `si` (in hex) after finishing loop L1?

Answer :

The SI register usually holds the address of a string or array, the ECX register acts as a counter for loops, and AL register may hold a character of a string or a byte of an integer. The values of these registers and memory locations depend on the precise code and inputs.

The answers to your questions depend on the exact ASM code being executed, but I can provide some general explanation to help you understand the concepts.

SI register typically holds the address of a string or array in memory and would change as different elements in the string or array are accessed.

The ECX register is often used as a counter for loop structures in assembly code, so its value would decrease with each iteration of loop L1 until it reaches zero and the loop ends.

The AL register, being the lower byte of the AX register, might hold a character of a string or a byte of an integer, depending on the particular code.

Without the actual source code, it's impossible to definitively say what the value of the target string in memory would be before and after the execution of the loop.

Similarly, for the program that sums an array of integers, the final sum, the number of iterations, and the final value of SI cannot be determined without specific information about the input and the exact coding implement.

To know more about loop structures visit:

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