In order to run the program, go to the folder Release and run project.exe.

Transcription

1 Assembly Language and System Software Lab exercise You need to implement seven programs. In this lab exercise, you are going to get familiar with assembly programming. You should follow the guideline to finish all the tasks. You may think about how to solve the problems before reading the guideline. Make sure that you compile and build the programs in Release mode. After building a program, an executable file is generated and the name of the file is project.exe. In order to run the program, go to the folder Release and run project.exe. If you modify your code, make sure you compile and build your program again. After finishing all the exercises, tell TAs and then you may leave.

2 p1. Write a program to ask a user to input three unsigned integers and then compute the sum of three unsigned integers. Print out the sum on the console window. We call ReadDec to read an unsigned integer to EAX. Then, we assign the value of EAX to another register. After we have all the three unsigned integers, we compute the sum and store it to EAX. For example, call ReadDec ; read an unsigned integer which will be stored in eax mov ebx, eax ; ebx = eax call ReadDec ; read an unsigned integer which will be stored in eax mov ecx, eax ; ecx = eax call ReadDec ; read an unsigned integer which will be stored in eax add eax, ebx ; eax = eax + ebx add eax, ecx ; eax = eax + ecx In order to print out an unsigned integer eax, we call writedec. call WriteDec After you finish the program, try the following data sets and check the result. Data set one: Input: 1, 2, 3 sum: 6 Data set two: Input: 0, 0, 0 sum: 0 Data set three: Input: 900, 80, 7 sum: 987 Data set four: Input: 1, 0, 0 sum:? Data set five: Input: 1, 2, 3 sum:? Could you explain why the incorrect results are obtained for the data sets four and five?

3 p2. Write a program to ask a user to input three signed integers and then compute the sum of three signed integers. Print out the sum on the console window. We call ReadInt to read a signed integer to EAX. Then, we assign the value of EAX to another register. After we have all the three signed integers, we compute the sum and store it to EAX. For example, mov ebx, eax ; ebx = eax mov ecx, eax ; ecx = eax add eax, ebx ; eax = eax + ebx add eax, ecx ; eax = eax + ecx In order to print out a signed integer in eax, we call WriteInt. call WriteInt Data set one: Input: 2, 3, 5 sum: +10 Data set two: Input: 2, 3, 5 sum: 10 Data set three: Input: 100, 20, 3 sum: +123 Data set four: Input: , , sum:? (9 zero digits) What is the sum for data set four? Could you explain why the result is obtained?

4 p3. In the previous programs, it is not easy to see that which integer is being entered. In order to let the user to know which integer is being entered, we can show a message on the screen. We call mwrite to do so. However, mwrite is defined in another file. In order to use mwrite, we need to include the file which defines macros. Make sure that you have the following two lines: INCLUDE Irvine32.inc INCLUDE Macros.inc ; this is the file which defines macros. Let s write a simple program to ask a user to input three signed integers and show them on the screen. For example, mwrite Please enter the first signed integer: mov ebx, eax ; ebx = eax mwrite Please enter the second signed integer: mov ecx, eax ; ecx = eax mwrite Please enter the third signed integer: add eax, ebx ; eax = eax + ebx add eax, ecx ; eax = eax + ecx mwrite The sum of the three signed integers is: call WriteInt Now, compile and build the program. After that try the following data sets: Data set one: Input: 0, 1, 2 sum: +3 Data set two: Input: 0, 1, 2 sum: 3 Data set three: Input: 123, 0, 123 sum: 0

5 p4. We can print out a value stored in EAX in different formats. Write a program to ask a user to input three unsigned integers and then compute the sum of three unsigned integers. Store the sum to EAX. Print out EAX with different formats on the console window. mwrite First signed integer: mov ebx, eax ; ebx = eax mwrite Second signed integer: mov ecx, eax ; ecx = eax mwrite Third signed integer: add eax, ebx ; eax = eax + ebx add eax, ecx ; eax = eax + ecx mwriteln The sum is (unsigned): call WriteDec mwriteln The sum is (signed): call WriteInt mwriteln The sum is (Hex): call WriteHex mwriteln The sum is (Binary): call WriteBinary mwriteln The sum is (Char): call WriteChar ; write AL as a ASCII code on screen Build and run the program. Data set one: Input: 1, 2, 4 Sum (in decimal): 1 Data set two: Input: 1, 0, 8 Sum (in decimal): 7 As you can see for the same value stored in EAX, we have different outputs on the console window. We interpret a value from different perspectives. Thus, make sure that you interpret a value correctly in a specific content.

6 p5. In this program, we draw a char on screen and make it move horizontally. We need an animation loop. The idea is stated as follows. An animation loop is as follows: clear the screen update the positions of objects draw objects at their current positions pause for a short period of time repeat To clear the screen, L1: call Clrscr ;here, we label this line. Later on, we can jump back to here. In our case, an object is a character which is stored in AL. We need to set the coordinates of the object and then draw it on screen. The coordinates of an object are defined as a pair (column, row). Thus, we define column and row in.data as follows: column BYTE 0 row BYTE 0 In order to update the position, we increase the column coordinate of the object: inc BYTE PTR column ; treat the content at column as one byte and increase its value by 1. Then, we set the position of the object to the current position: mov dl, column mov dh, row call Gotoxy ; set the cursor position to (dl, dh) After that we draw the object (i.e., a char) as follows: mov al, A call WriteChar In order to pause the program for a while, we do the following: mov eax, 10; // in milliseconds call Delay Thus, there is one second delay if we do the following: mov eax, 1000; // in milliseconds call Delay Finally, we jump back to the beginning of the animation loop, i.e., jmp L1. Build your program and check it. You can find the solution in the solution folder. Do you see something that does not look well? The character is blinking while it s moving!

7 p6. Let s do something better than p5. We want to show an introduction message and then enter the animation loop. We have the followings: L0: show an introduction message L1: save the current positions of objects L2: update the positions of objects L3: draw objects (with the background color) at their old positions L4: draw objects (with their own colors) at their current positions L5: pause for a short period of time L6: constrain the positions of the objects within certain ranges repeat L1 L6 In this modified animation loop, we do not clear the screen anymore. Instead, we draw the objects twice but with different colors. When we draw the objects with background at the first time, we clear the regions that were covered by the objects. In the following, let s finish the items one by one. Define data:.data curx BYTE 0 ; current column cury BYTE 0 ; current row oldx BYTE 0 ; old column oldy BYTE 0 ; old row L0: show an introduction message call Clrscr mwriteln This is a simple animation written by XYZ. mwriteln Press a key to continue. Call ReadInt call Clrscr ; clear the screen before starting the animation L1: save the current positions of objects mov al, curx mov oldx, al mov al, cury mov oldy, al L2: update the positions of objects inc PTR BYTE curx L3: draw objects (with the background color) at their old positions mov dl, oldx mov dh, oldy call GotoXY

8 mov al, 0 call SetTextColor mov al, A call WriteChar L4: draw objects (with their own colors) at their current positions mov dl, oldx mov dh, oldy call GotoXY mov al, blue ; call SetTextColor ; set text color mov al, A call WriteChar L5: pause for a short period of time mov eax, 20 call Delay In order to make the x coordinate of the object lie within an interval, e.g., [0, 60], we add the following lines immediate after inc PTR BYTE curx : mov al, curx cmp al, 60 jna L2 mov al, 0 mov curx, al L2: Question: What happens if you add the above 6 lines after call Delay. After that we write: jmp L1 ; go to the L1 Build and run the program. You can see the motion blur of the character. There is no blinking anymore. You may use different colors to draw the character.

9 P7. We extend p6 to show characters with different colors (e.g., white, yellow and cyan). In each row, we show a character moving from the left to the right. If the x coordinate of an object is greater than 60, make it move from 0. You can assume that there are three characters and each character moves in one row. 1. Convert each item into a procedure. Give a meaningful name to each procedure. 2. Then, we have the followings: L1: call ShowIntroduction call SaveCurrentPositions call UpdateObjectPositions call DrawObjectsAtOldPositions call DrawObjectsAtCurrentPositions call DelayForAPeriod jmp L1 As you can see, we perform the tasks one by one and each task is associated with one procedure. Your code is very readable. At the end of each procedure, we must write down ret. For example, ShowIntroduction PROC call Clrscr mwriteln This is a simple animation written by XYZ. mwriteln Press a key to continue. Call ReadInt call Clrscr ; clear the screen before starting the animation ret ; return to the caller ShowIntroduction ENDP SaveCurrentPositions PROC ; we need three pairs of coordinates for three objects ; later on, we can use array and loop structure handle the following tedious data structure mov al, curx01 mov oldx01, al mov al, cury01 mov oldy01, al mov al, curx02 mov oldx02, al mov al, cury02

10 mov oldy02, al mov al, curx03 mov oldx03, al mov al, cury03 mov oldy03, al ret SaveCurrentPositions ENDP DelayForAPeriod PROC mov eax, 20 call Delay ret DelayForAPeriod ENDP Please convert the other tasks into procedures. You can find the solution in the solution folder. After you are done, add call Clrscr immediately after L1. Run the program again. You will see the moving characters which are blinking heavily. Note: After you have finished all the programs, ask yourself what you have learnt. Enjoy.