pTAL Reference Manual (H06.08+)

Data Representation

HP pTAL Reference Manual—523746-006

3-20

REAL and REAL(64) Numeric

Examples of REAL and REAL(64) numeric constants, showing the integer part, the

fractional part, the E or L suffix, and the exponent part:

The system stores the number in binary scientific notation in the form:

x * 2

x is a value of at least 1 but less than 2. Because the integer part of x is always 1, only

the fractional part of x is stored.

The exponent can be in the range -256 through 255 (%377). The system adds 256

(%400) to the exponent before storing it as y. Thus, the value stored as y is in the

range 0 through 511 (%777), and the exponent is y minus 256.

If the value of the number to be represented is zero, the sign is 0, the fraction is 0, and

the exponent is 0.

The system stores the parts of a floating-point constant as follows:

Examples of storage formats:

1. For the following REAL constant, the sign bit is 0, the fraction bits are 0, and the

exponent bits contain %400 + 2, or %402:

4 = 1.0 * 2

stored as %000000 %000402

2. For the following REAL constant, the sign bit is 1, the fraction bits contain %.2

(decimal .25 is 2/8), and the exponent bits contain %400 + 3, or %403:

-10 = -(1.25 * 2

) stored as %120000 %000403

3. For the following REAL(64) constant, the sign bit is 0, the fraction bits contain the

octal representation of .33333..., and the exponent bits contain %400 - 2, or %376:

1/3 = .33333…* 2

-2

stored as %025252 %125252 %125252 %125376

Decimal Value REAL REAL(64)

0 0.0E0 0.0L0

22.0e0

0.2E1

20.0E-1

2.0L0

0.2L1

20.0L-1

-17.2 -17.2E0

-1720.0E-2

-17.2L0

-1720.0L-2

Data Type Sign Bit Fraction Exponent

REAL <0> <1:22> <23:31>

REAL(64) <0> <1:54> <55:63>