CSE306 Homework 3

CSE306 Processing Systems and Structures Lockwood, Spring 2003

Homework Assignment 3

Due: Monday March 24, 2003, 5pm

75 Points

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ID Important: Use the same ID as selected in HW0
Name (First Last)

Homework Questions

    Text-Mode Video

    For each of the elements that we wish to display on an 80x25 text-mode screen, determine the attribute (AH), character (AL), and offset (DI) into video memory that must be established before we execute the following code:
    Specify all numbers in hex.

    MOV DX, 0B800h MOV ES, DX MOV ES:[DI],AX

    The letter 'J' in blue on a black background at row 0, column 3.

  1. AX= (2 pts)
  2. DI= (1 pt)

    The letter 'L' in (intense) white on a green background at row 3, column 3.

  3. AX= (2 pts)
  4. DI= (1 pt)

    A magenta (purple) heart on a black background at row 10, column 54.

  5. AX= (2 pts)
  6. DI= (1 pt)

    An intensely-colored green clover on a black background on the third text-mode video page (page 2) at row 2, column 3.

  7. AX= (2 pts)
  8. DI= (1 pt)

    A blinking, empty, black, smiley character on a purple (red+blue) background on the fourth text-mode video page (page 3), at the lower-righthand corner of the screen.

  9. AX= (2 pts)
  10. DI= (1 pt)

    Table-Lookup Functions

    Consider the following code that uses a table-lookup function to efficiently encode and decode top-secret messages.

    ; ------- Data Section ------- InputString db 'RPR291*VF*SHA','$' OutputString db ' ','$' TableFunction db 'NOPQRSTUVWXYZABCDEFGHIJKLM' ... ; ------- Code Section ------- MOV SI, 0 MOV BH, 0 ConvLoop: MOV BL,InputString[SI] CMP BL,'$' JE ConvDone CMP BL,'Z' JA ConvNext CMP BL,'A' JB ConvNext MOV BL,TableFunction[BX-'A'] ConvNext: MOV OutputString[SI], BL INC SI JMP ConvLoop ConvDone: ...

    After running the program, OutputString =

  11. (10 pts)

    Jump Tables

    Consider the following code that uses a jump table to recursively call itself. Find the values of Result after calling the Main program. Calculate the five elements of Result[] in decimal (base 10).

    Result db 5 dup(5) Main PROC FAR mov ax,cseg mov ds,ax MOV CX,5 MLoop: MOV DI,CX SHL DI,1 MOV SI,CX Call JFunct LOOP MLoop call dosxit ; Exit to DOS Main ENDP JTable dw offset F0 dw offset F1 dw offset F2 dw offset F3 dw offset F4 dw offset F5 JFunct PROC NEAR JMP JTable[DI] F0: ADD Result[SI],103 RET F1: DEC Result[SI] RET F2: OR Result[SI],8 ADD DI,2 Call JFunct SUB Result[SI],12 RET F3: SHL Result[SI],1 SUB DI,6 Call JFunct RET F4: XOR Result[SI],17 RET F5: ADD Result[0],64 RET JFunct ENDP

  12. Result[0]= (decimal) (3 pts)

  13. Result[1]= (decimal) (3 pts)

  14. Result[2]= (decimal) (3 pts)

  15. Result[3]= (decimal) (3 pts)

  16. Result[4]= (decimal) (3 pts)

    DOS/BIOS/vBIOS Calls

    The BIOS (Basic I/O System), vBIOS (Video BIOS), and DOS provide a number of useful functions available through interrupt vectors. To use these commands, the opcode INT n is used to trigger the software interrupt. Using your lab manual, textbook, or lecture notes; determine what values are necessary to perform the following actions. Specify all numbers in hex.

    vBIOS call to display the third video page (page 2) on the screen.

  17. AX = (hex) ( 2 pts )
  18. INT (hex) (1 pt)

    Mouse-driver function that determines cursor position and status of mouse buttons

  19. AX = (hex) ( 2 pts )
  20. INT (hex) (1 pt)

    BIOS call to check to see if keyboard input is available. Sets ZeroFlag=1 if nothing is available.

  21. AH = (hex) ( 2 pts )
  22. INT (hex) (1 pt)

    DOS call to read system date (day of week, year, month, day of the month)

  23. AH = (hex) ( 2 pts )
  24. INT (hex) (1 pts)

    DOS call to open a file (preferred method)

  25. AH = (hex) ( 2 pts )
  26. INT (hex) (1 pt)

    Hardware Interrupt vector number called when a character is received from the serial port on IRQ3

  27. INT (hex) (2 pts)

    Hardware Interrupt vector number called when a SCSI controller on IRQ13 interrupts the system.

  28. INT (hex) (2 pts)

    Hash Tables

    Suppose we write a program which counts the number of incoming IP packets on a network link from hosts scattered throughout the Internet. Each host has a unique 32-bit source address which is encoded in the packet. We will use a 256-entry hash table and the following hash function to quickly map an IP address to a table entry:

    H(X1.X2.X3.X4) = X2 xor X4
    where the X1.X2.X3.X4 is the IP source address

    Linear probing is used when a collision occurs. When a new packet arrives; it's address is mapped to the first available (unused) entry starting at the hash location, and the count is set to one. When a packet arrives that is already in the hash table, the corresponding counter is incremented.

    Determine the hash address for the following stream of IP packets (Suggestion: Use a calculator to determine the hash addresses). Increment the value of count as packets from the same host arrive. Enter all numbers in decimal (base 10).

    Questions 29-44:
    Hash
    Entry
    (0..255)    		IP AddressNew
    Count
    		30. 128.174.114.171
    		32. 128.174.5.49
    		34. 141.142.21.17
    		36. 128.174.5.49
    		38. 141.142.171.114
    		40. 128.174.114.171
    		42. 141.142.21.17
    		44. 141.142.171.114
    45. (1 point/question )

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