Homework 4 - Structured Programming

Programming Assignment 4 and Hints

1. Although there are simpler algorithms, please use the algorithm below for determining whether a number is a palindrome.
• To understand the algorithm behavior, compile and execute the C++ or Pascal algorithm.
• Your program should behave the same as the C++ or Pascal algorithm.
• Note that some numbers (e.g. unsigned numbers greater than 2147483647 are treated as negative) will cause the algorithm to fail.
2. Write the Assembly language program using structured techniques discussed in class to determine if a given unsigned 32-bit integer is a palindrome.
3. Document your program following the examples given in class or from the text of Chapter 4.
4. Turn in
1. Cover Page - Your name, date, and Homework 4. Staple all pages together.
2. Assembler program (what you typed in).
3. Input: 1234, 1221, 12321, 43234, 65456, 214747412, 2147483647, 0. The 0 input terminates the program.
4. Output: Print whether input number is a palindrome or not a palindrome with the exception of the 0.

• Use 32-bit unsigned arithmetic. Remember what to do to eDx prior to performing unsigned division with a 32-bit divisor.
• To print a carriage return line feed at the end of a string use:
 
Palindrome   db  'Palindrome', 0, 10, 13

Lea        eDx,  Palindrome
Call       WriteString

{ Input integer and determine if a palindrome until 0 entered }
Var AB, BA : Integer;         { Numbers to test if palindromes }
    Q      : Integer;         { Quotient of division by 10 }
Begin
   Repeat
     Writeln('Enter unsigned 16-bit integer:');
     Read( AB );
     If AB > 0 Then
     BEGIN
          BA := 0;
          Q := AB;
          While Q <> 0 Do          { Reverse AB to BA }
          BEGIN
               BA := BA * 10;      { Shift BA left 1 digit }
               BA := BA + Q Mod 10;{ Right digit of Q = left BA }
               Q := Q Div 10;      { Drop right digit }
          END;
          If AB=BA Then            { If Reversal = Forward  }
             Writeln('Palindrome') {    Then Palindrome     }
          Else Writeln('Not Palindrome');
     END;
 Until AB = 0;
End.

C++ Algorithm

// Input integer and determine if a palindrome until 0 entered
#include <iostream.h>
void main () {
   int AB, BA;           // Numbers to test if palindromes
   int Q;                // Quotient of division by 10
   do {
     cout << "Enter unsigned 16-bit integer:";
     cin >> AB;
     if (AB > 0) {
       BA = 0;
       Q = AB;
       while ( Q != 0 ) {            // Reverse AB to BA
           BA = BA * 10;             // Shift BA left 1 digit
           BA = BA + Q % 10;         // Right digit of Q = left BA
           Q = Q / 10;               // Drop right digit
       }
       if (AB==BA)                   // If Reversal == Forward
          cout <<  "Palindrome\n";     //   Then Palindrome
       else cout << "Not Palindrome\n";//   Else Not Palidrome
     }
  } while (AB != 0); 
}

Using Visual Studio Debugger with Assembler

The Visual Studio debugger can be used to debug 32-bit Assembler executable programs.

1. Start Visual Studio .NET
2. File | Open | Project
3. HelloWorld.exe
4. Press F10 key to open the HelloWorld.asm file and start execution.
5. Save the solution. Required before .NET will continue.
6. In the figure at right, the arrow point to the next instruction to execute. Passing the mouse pointer over eCx in the assembly code displays the value of eCx=11.

• To execute the complete program enter F5.
• A black console window will open where input/output is performed.

• File | Close Solution

• Step into function - F11.
• Step around function - F10.
• Execute to cursor - Put cursor on line and press Ctrl F10.
• Watch variable - Put cursor over variable or register, or click right mouse button, then QuickWatch.
• View memory - Click View | Debug Windows | Memory. Type in the memory address or a register that references memory. The figure at right display the contents of memory referenced by the eDi register.
• Stop debugging - Ctrl F5.