REVISED LAB 2

Due January 26, 9PM

Multi-base conversion

Graded assignment; all work must be strictly your own.  Do not show or
describe your program to other students.  On this assignment, you may
discuss programming issues along the lines of "I don't know how
procedures work" answered with examples unrelated to this assignment.
You can use the text (or talk to myself or a TA) if you do not
understand base conversion.

The conversion program will input bases and numbers and output them in
base 10.  Next week, we'll revisit the adding machine.

All numbers entered are unsigned.

The system will work with bases greater than or equal to 2.

a.  Numbers will use Commas to separate "digits".  A "digit" has
    several characters, each 0-9, such that their positional
    representation is less than the base.  For example:
    0,12,0,59.  You will have to read these in character by character
    (see text), since get reads in one number per line, and we want
    several on a line.
c.  The output format is base 10 (use put on .words)


<<Informatively prompt user to enter numbers or commands>>
<<Enter base: >>10
<<Enter number:>>1,0
<<= 10 (base 10)>>
<<Enter base: >>2
<<Enter number: >>1,0
<<= 2 (base 10)>>
<<Enter base: >>2
<<Enter number: >>1,1,1,0
<<= 14 (base 10)>>
<<Enter base:>> 60
<<Enter number: >>10,12
<<= 612 (base 10)>>
<<Enter base: >>0
<<Thank you for using the 12C base converter!>>

Notes:

1.  Write your own get character procedure that ignores spaces.
    All input should be character by character.

2.  Write a digit reading routine that will read a complex digit.

    In reading digits, you will want to read characters and convert to
    base 10 until you see a ',' or newline.  The resulting base 10
    number (between 0 and base-1) will then be used to form the user's
    number (part 3).

    The digit reading routine will need a special way to indicate that
    a newline has been detected (ie, there is no trailing ,), perhaps
    by maintaining the last character read in a place readable by
    other routines.  If it's a comma, there is still more input to the
    number; if a newline, the number is done.

3.  Your number reading routine will call the digit reading routine
    and do the appropriate multiplies and adds to form an internal
    representation of the integer typed in.

4.  Error messages and prompts are important:  what errors can
    come up?  A few are illustrated above.  You are encouraged to use
    different prompts and error messages.

6.  The main program will be a loop of enter base commands/enter
    number commands.  If an invalid base is entered, the program will
    exit. 

Minimally, you must have separate, well-structured PROCEDURES using LA
for: 
   a. Reading the next character ignoring spaces
   b. Reading a comma/newline delimited "digit"  (which calls (a))
   c. Reading an unsigned number and converting to internal form
      according to base (which calls b).


HANDIN:

convert.spim
README
    a.  Name and email address
    b.  Overview of your code
    c.  Thoughts on what you will need to change in your code
        to work with negative numbers
    d.  Any other comments on SAL and SPIM.

Points:  10 points maximum

	 Basic functional program:  7 points

	 Comments:
	   -5     None
	   -1..-2 Poor
           +1/2   Excellent comments and README

	 User interface:
	   -1   None
           +1   Excellent prompts and user interface

	 Error messages:
           +1/2 Some error messages
	   +1   Excellent error messages

	 Extra stuff:
	   +1   Input negative numbers as well

	 Coding:
	   +1/2   Incredible code 
	   -1..-3 Confusing control structures, variables, and the like.

	 Procedures
	   -5     No procedures 
	   -1..-2 Poorly structured procedures