CSE 320 Fall 2018
Computer Project #6
Assignment Overview
This assignment develops familiarity with the C programming language, the "gcc" compiler, integer bitwise
operations, and floating point representation and arithmetic.
It is worth 40 points (4% of course grade) and must be completed no later than 11:59 PM on Thursday, 10/18.
Assignment Deliverables
The deliverables for this assignment are the following files:
proj06.makefile – the makefile which produces "proj06"
proj06.support.c – the source code for your support module
proj06.driver.c – the source code for your driver module
Be sure to use the specified file names and to submit them for grading via the CSE handin system before the
project deadline.
Assignment Specifications
Some computer systems do not have floating point hardware: they have an Integer Unit, but not a Floating Point
Unit. Thus, floating point operations on those systems must be performed using software.
1. You will develop the C function listed below:
double add( double, double );
The two arguments are the double precision floating point values to be added, and the return value is the sum of
those two values. The sum will be as accurate as possible.
Arguments which are denormal will be processed as the value zero.
If either argument is the floating point value "not-a-number", function "add" will return that value. Otherwise, if
either argument is the floating point value "infinity", function "add" will return that value.
Function "add" (and any associated "helper" functions which you develop) will constitute the support module. The
functions in that support module will not call any C library functions, and they will not use any floating point
operations. There is one exception: the functions may use the assignment operation to copy a floating point value
from one variable to another.
2. You will develop a driver module to test your implementation of the support module. The driver module will
consist of function "main" and any additional helper functions which you choose to implement. All output will be
appropriately labeled.
Assignment Notes
1. Your driver module and your support module must be in separate source code files.
2. Your source code must be translated by "gcc", which is a C compiler and accepts C source statements.
3. You must supply a "makefile" (named "proj06.makefile"), and that makefile must produce an executable
program named "proj06".
4. Your driver module may not be written as an interactive program, where the user supplies input in response to
prompts. Instead, your test cases will be included in the source code as literal constants.
5. The Harris and Harris textbook contains information about IEEE floating point representation and operations
(section 5.3.2).
Please note that infinity, not-a-number, zero and denormal numbers are special cases in IEEE floating point
notation.
6. An outline of one method for computing C = A + B is given below:
Extract sign, exponent, and fraction fields of both A and B.
Place leading bit in both significands.
Determine exponent of C based on exponents of A and B; shift significand of A or B
(based on the difference between exponents).
Compute significand of C = significand of A + significand of B.
Normalize significand of C.
Insert sign, exponent, and fraction fields of C.
Note that this outline does not describe special cases, such as operands which are infinity, not-a-number, zero or
denormal numbers.
7. In order to work with a 64-bit item as both a floating point value and an integer value, you might consider using
a union. For example:
#include
union double_precision
{
double drep;
unsigned long long int irep;
};
int main()
{
union double_precision num;
num.drep = 1.5;
printf( "Real: %f Hex integer: %016llx \n", num.drep, num.irep );
}
When compiled and executed, that program produces the following:
Real: 1.500000 Hex integer: 3ff8000000000000
Note that the eight-byte memory location "num" can be referenced as both an object of type "double" and an
object of type "unsigned long long int".