Programming Laboratory III: calculating a string expression

Programming Laboratory III: Calculating a String Expression

Absolutely no copying others' work
Due Dates

Monday, October 27, 2008 in class, or
Monday, October 20^th or Tuesday, October 21^st in labs.

The Objectives
This lab is an extension of the Lab 2. Design and implement an assembly program which calculates a string expression. Students learn how to use various control structures and maybe procedures from this lab, which is about 150 lines long.

Submission Methods
Turn in hard-copy assembly code and apply either one of the following two methods:

Post the assembly code at http://people.cs.und.edu/~userid/250/ .
Turn in a CD labeled with your name and lab3.asm .

The Problem (Calculating a String Expression)
Write a program that calculates a string expression, which includes two binary operators:

+: string concatenation. For example, "abc" + "xyz" = "abcxyz" .
/: string removal. It removes the first occurrence of the pattern from the string. For example, "abcxyz" / "cx" = "abyz" and "xabyabz" / "ab" = "xyabz" .

Both operators are left associative and have the same precedence. No error checking is required, i.e., assume the input is always correct. The following list shows some execution examples:

Examples of Laboratory 3 Execution

 
C:\250\lab\3\Debug> Project

Enter the expression: "abc" + "xyz"
 
The result is "abcxyz" 
 
 
C:\250\lab\3\Debug> Project 
 
Enter the expression: "abc"+   "" 
 
The result is "abc" 
 
  
C:\250\lab\3\Debug> Project
 
Enter the expression:    "abxycd" / "xy" 
 
The result is "abcd" 
 
  
C:\250\lab\3\Debug> Project 
 
Enter the expression:    "abxycd" / "" 
 
The result is "abxycd" 
 
 
C:\250\lab\3\Debug> Project 
 
Enter the expression:    "" / "abcd"  
 
The result is ""
 
 
C:\250\lab\3\Debug> Project
 
Enter the expression: "abxycd"/"xyz" 
 
The result is "abxycd" 
 

C:\250\lab\3\Debug> Project
 
Enter the expression: "abc" + "xyz" / "cx" 
 
The result is "abyz" 

 
C:\250\lab\3\Debug> Project
 
Enter the expression: "aa" / "a" + "bb" / "b" + "cc" / "c"
 
The result is "abc"
 
 
C:\250\lab\3\Debug> Project
 
Enter the expression: "Thisis is only" / "is" + " a test." 
 
The result is "This is only a test." 

 
C:\250\lab\3\Debug> Project 
 
Enter the expression: "This is " + "only" + "a test a test." / " a test" 
 
The result is "This is onlya test."

where the italic text with a yellow background is entered by users.

Possible Instructions Used
The following operators, directives, and commands may be used in this lab:

No.	Operators/ Directives/ Commands	Description	Textbook Page Numbers
1	`add`	Addition	87 – 88
2	`BYTE`	Directive of defining byte	66 – 67
3	`call`	Calls a procedure by directing the processor to begin execution at a new memory location.	136
4	`call Crlf`	Writes an end of line sequence to standard output.	115
5	`call ReadString`	Reads a string from the keyboard, stopping when the user presses the `Enter` key.	122
6	`call StrLength`	Returns the length of a string in `EAX`. Pass the string's offset in `EDX`.	123
7	`call WriteChar`	Writes a single character to standard output. Place the character in `AL` before calling the procedure.	123
8	`call WriteString`	Writes a null-terminated string to standard output. When calling it, place the string's offset in `EDX` register.	124
9	`cmp`	Performs an implied subtraction of a source operand from a destination operand.	156
10	`.code`	Marks the beginning of the code segment.	55
11	`.data`	Marks the beginning of the data segment.	55
12	`dec`	Decrement	87
13	`DUP`	Generates a repeated storage allocation, using a constant expression as a counter.	67
14	`DWORD`	Directive of defining doubleword	68
15	`END`	Marks the last line of the program to be assembled.	59
16	`ENDP`	Marks the end of a procedure.	59
17	`exit`	Calls a predefined MS-Windows function that halts the program.	59
18	`.IF .ELSEIF .ELSE .ENDIF`	`IF` statement	184 – 186
19	`inc`	Increment	87
20	`INCLUDE Irvine32.inc`	Copies necessary definitions and sets up information from a text file name `Irvine32.inc`, located in the assembler's `INCLUDE` directory.	59
21	`je`	Jumps if equal	158 – 162
22	`jmp`	Causes an unconditional transfer to a target location inside the code segment.	104
23	`jne`	Jump if not equal	158 – 162
24	`loop`	Loop. `ECX` is automatically used as a counter and is decremented each time the loop repeats.	105 – 106
25	`mov`	Move	81 – 82
26	`OFFSET`	Returns the offset of a data label.	94
27	`PROC`	Identifies the beginning of a procedure.	59
28	`PROC ... USES`	Lists the names of all registers modified within a procedure.	140 – 142
29	`PTR`	Overrides the declared size of an operand.	95 – 96
30	`ret`	Pops the return address from the stack into the instruction pointer.	135 – 136
31	`SIZEOF`	Size of a data item	97
32	`sub`	Subtraction	88

Evaluation
The following features will be considered when grading:

This lab will not be graded if the system interface can not be found at http://people.cs.und.edu/~userid/250/ or a CD is not submitted. For security, perform the following operation:
```
  gandalf> chmod 700 lab?.asm*
```
to block all read/write accesses from others to the files lab?.asm* . Firefox will be used to download code. Be sure your system is working on Firefox 3.0 or above.
Microsoft MASM 8.0 assembler will be used to grade labs. Make sure your labs work on MASM 8.0.
Before submitting the lab, test it comprehensively. Absolutely no extra points will be granted after grading.