605.202 Data Structures LAB 1
Use of Stacks
Assume a Machine has a single register and six instructions (Problem 2.3.10 from the LAT text.)
LD A places the operand A in the register
ST A places the contents of the register into the variable A
AD A adds the contents of the variable A to the register
SB A subtracts the contents of the variable A from the register
ML A multiples the contents of the register by the variable A
DV A divides the contents of the register by the variable A
Write a program that accepts a postfix expression containing single letter operands and the
operators +, -, *, and / and prints a sequence of instructions to evaluate the expression and leaves
the result in the register. Use variables of the form TEMPn as temporary variables. For example,
using the postfix expression ABC*+DE-/ should print the following:
LD B
ML C
ST TEMP1
LD A
AD TEMP1
ST TEMP2
LD D
SB E
ST TEMP3
LD TEMP2
DV TEMP3
ST TEMP4
Use the following postfix expressions for input
AB+C- ABC+/CBA*+
ABC+- AB-*CBA+-*
AB-C+DEF-+$ ABC-/BA-+/
ABCDE-+$*EF*- ABC+$CBA-+*
ABC+*CBA-+* AB0+/CBA+-/
Keep in mind that you are NOT evaluating the postfix expression, you are generating the machine
language instructions that would perform the evaluation if actually executed.
In your analysis, be sure to discuss the implementation you choose and why, why a stack makes
sense. Consider a recursive solution (you do not need to implement recursion) and compare it to
your iterative solution. Is one better than the other? Why? Tell us what you learned and what you
would do differently. Be sure to review the programming assignment guidelines, including the
formatting requirements for the analysis. You may not use library functions. You must write your own
code, in particular you must write the stack code. Be sure to include the stack source code in your
suibmission. You must read and write from named files.
