CS 061 – Computer Org. & Assembly Lang. Fall - 2004
Assignment 4 - due Thursday 10/21, 11 pm
Instructions:
Turn in your source code (.asm file) to the folder assn:
Remember to include your personal header (name, id, team partners, etc.)
Synopsis
Enter a multi-digit decimal integer at the keyboard, and translate it into 16-bit 2’s complement
binary for storage in the computer.
Description
WARNING: you will not be able to handle this assignment until you have completely understood
assignment 3!
Prompt the user to enter a 4 digit decimal integer (positive or negative) at the keyboard, and produce
the following outputs to the console:
a) the number as entered (i.e. echo the input to the console);
b) the 16-bit 2’s complement binary representation of the number ;
You must check each of the input digits to see if it is a valid number component, i.e. '0' to '9' (x30 to
x39), or '+' (x2B) or '–' (x2D); If not, disregard the whole input, and output an error message.
You may require that the input number be always 4 digits (i.e. 27 must be input as 0027), but this is not
the preferred solution.
Some tips:
Experiment with TRAP x20 (GETC) and TRAP x21 (OUT) to make sure you understand exactly
how they work.
The CR/LF (newline) character is ASCII x0A.
store the negative of the ASCII values for '+' and '-' and '0' and '9' to simplify testing (why?)
if the number is negative (i.e. if the first character entered is '-'), you will need to flag that fact so as
to take the 2's complement after translating the number into binary.
set up a .BLKW #4 to store the entered digits (this makes it easier to separate data entry &
verification from the conversion processing).
you already know how to extract the binary integer corresponding to each decimal symbol ('0' to '9'):
what is the "weight" of each succeeding digit in the decimal number? (Note: there are a couple of
ways of doing the conversion to binary - by column weight, as suggested, or by lookup table. Think
about both & choose whichever you like).
you already know how to print out a binary number as a series of ASCII ‘1’s and ‘0’s
Make sure you have complete and consistent comments in your code.
