iFloat.h File Reference

Defines interface of iFloat.c functions (do not modify) More...

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Macros
#define	HALF
#define	BITS   16
#define	BITS_EXP   5
#define	BITS_MANT   10
#define	EXP_BIAS   15

Typedefs
typedef short	iFloat_t

Functions
iFloat_t	floatGetSign (iFloat_t x)
iFloat_t	floatGetExp (iFloat_t x)
iFloat_t	floatGetVal (iFloat_t x)
void	floatGetAll (iFloat_t x, iFloat_t *sign, iFloat_t *exp, iFloat_t *val)
iFloat_t	floatLeftMost1 (iFloat_t bits)
iFloat_t	floatAbs (iFloat_t x)
iFloat_t	floatNegate (iFloat_t x)
iFloat_t	floatAdd (iFloat_t x, iFloat_t y)
iFloat_t	floatSub (iFloat_t x, iFloat_t y)

Detailed Description

This file defines the interface to a C file iFloat.c that you will complete. You will learn how to do floating point arithmetic without using any float variables. Rather you will perform the operations by using the sign, exponent, and digit fields as defined in the IEEE Floating Point Standard.

Everything in a computer is stored as a series of 0/1's. When you use an int to type a value, you are telling the compiler (and ultimately the CPU) to treat the 0/1's as a two's complement number. When you use float, the 0/1's represent a floating point number. When an addition is performed, the computer knows whether to use the integer or floating point add instruction. The two instructions do different things to the 0/1's.

In this assignment, you are doing floating point operations without using floating point instructions. You are directly doing the bit manipulations necessary to complete the add. Since iFloat_t is an integral type, the compiler will generate integer instructions. The iFloat_t is to remind you (the programmer), that although the computer is going to treat all values as integers, you know it is really 3 values (sign, exponent, mantissa) packed into a single integer number. Your responsibility is to unpack the three pieces, do the operations necessary to complete the operation, then put the three pieces back together.

Function Documentation

iFloat_t floatAbs

(

iFloat_t

x

)

Absolute value of the argument. This can be done with a simple bit manipulation operation. No conditionals are required.

Parameters

x	the integer containing an IEEE floating point value

Returns

the absolute value of the parameter

Todo:

Implement based on documentation contained in iFloat.h

iFloat_t floatAdd	(	iFloat_t	x,
		iFloat_t	y
	)

Add two floating point values.

Parameters

x	an integer containing an IEEE floating point value
y	an integer containing an IEEE floating point value

Returns

x + y. Your code needs to account for a value of 0.0, but no other special cases (e.g. infinities).

Todo:

Implement based on documentation contained in iFloat.h

void floatGetAll	(	iFloat_t	x,
		iFloat_t *	sign,
		iFloat_t *	exp,
		iFloat_t *	val
	)

Get the sign, exponent, and value in a single call.

Parameters

x	the integer containing an IEEE floating point value
sign	pointer to location where the sign will be stored
exp	pointer to location where the exponent will be stored
val	pointer to location where the value will be stored

Todo:

Implement based on documentation contained in iFloat.h

iFloat_t floatGetExp

(

iFloat_t

x

)

Extract the exponent of the argument.

Parameters

x	the integer containing an IEEE floating point value

Returns

the biased exponent of the argument

Todo:

Implement based on documentation contained in iFloat.h

iFloat_t floatGetSign

(

iFloat_t

x

)

Extract the sign of the argument.

Parameters

x	the integer containing an IEEE floating point value

Returns

0 if the value is 0 or positive, 1 if it is negative

Todo:

Implement based on documentation contained in iFloat.h

iFloat_t floatGetVal

(

iFloat_t

x

)

Extract the value of the argument. The value is the mantissa with the implicit 1 made explicit and adjusted for the sign of the argument. Please refer to the floating point addition example (step 1) in the instructions for an example on how the value is extracted. Basically, you'll have to do three things: 1) extract the mantissa; 2) set the implicit 1 in the extracted mantissa; 3) if the sign of the argument is negative, return the 2's complement of the mantissa from step (2). Otherwise, return it as-is. You may want to use the getField function from R3.

Parameters

x	the integer containing an IEEE floating point value

Returns

the bits representing the value. If x represents 0.0, you should still set the implicit 1 in the extracted mantissa.

Todo:

Implement based on documentation contained in iFloat.h

iFloat_t floatLeftMost1

(

iFloat_t

bits

)

Obtain the position of the leftmost 1 in the argument's bits.

Parameters

bits	the integer

Returns

-1 if the value is 0, otherwise the position (0 to 15) of the leftmost 1 bit. In a binary number, the positions are numbered from right to left with the rightmost position being 0.

Todo:

Implement based on documentation contained in iFloat.h

iFloat_t floatNegate

(

iFloat_t

x

)

Negate the argument. This can be done with a simple bit manipulation function. No conditionals are required. This is NOT the bitwise negation of the argument. As an example, if the argument represents 2.25, this function should return the IEEE bit pattern for -2.25.

Parameters

x	the integer containing an IEEE floating point value

Returns

the negation of the value. Note that the negation of 0.0 is 0.0 (not -0.0).

Todo:

Implement based on documentation contained in iFloat.h

iFloat_t floatSub	(	iFloat_t	x,
		iFloat_t	y
	)

Subtract two floating point values.

Parameters

x	an integer containing an IEEE floating point value
y	an integer containing an IEEE floating point value

Returns

x - y. Your code needs to account for a value of 0.0, but no other special cases (e.g. infinities).

Todo:

Implement based on documentation contained in iFloat.h