Exit: The two-byte signed two's complement representation of the integer portion is left in M1 (high-order byte) and M1+1 (low-order byte). The floating point values +24.63 and -61.2 are converted to the integers +24 and -61 respectively. FP1 and E are altered but FP2, E, SIGN, and SCR are not. The A- and X-REGs are altered but the Y-REG is not.

Example: The floating point value +274 is in FP1 prior to calling FIX.

 

_____

 

_____

 

_____

 

_____

FP1:

$88

$44

$80

0 (+274)

_____

_____

_____

_____

X1 M1

After calling FIX, M1 (high-order byte) and M1+1 (low-order byte) contain the integer representation of +274 ($0112).

 

_____

 

_____

 

_____

 

_____

FP1:

$8E

$01

$12

0

_____

_____

_____

_____

X1 M1

Note: FP1 contains an unnormalized representation of +274 upon exit.

NORM Subroutine (address $F463)

Purpose: To normalize the value in FP1, thus insuring maximum precision.

Entry: A normalized or unnormalized value is in FP1.

Exit: The value in FP1 is normalized. A zero mantissa will exit with X1=0 (2 exponent). If the exponent on exit is -128 (X1=0) then the mantissa (M1) is not necessarily normalized (with the two high-order mantissa bits unequal). E, FP2, SIGN, AND SCR are not distubed. The A-REG is disturbed but the X- and Y-REGs are not. The carry is set.

Example: FP1 contains +12 in unnormalized form (as .0011 x 2 ).

 

_____

 

_____

 

_____

 

_____

 

 

FP1:

$86

$0C

0

0

(+12)

_____

_____

_____

_____

 

x1 M1

Upon exit from NORM, FP1 contains +12 in normalized form (as 1.1 x 2 ).

 

_____

 

_____

 

_____

 

_____

FP1:

$83

$60

0

0 (+12)

 

 

 

 

 

 

 

 

Page 76
Image 76
Apple II manual

II specifications

The Apple II, launched in April 1977, was one of the first highly successful mass-produced microcomputer products. It marked a significant leap in personal computing, setting standards for future developments in the industry. Created by Steve Wozniak and Steve Jobs, the Apple II differentiated itself with its user-friendly design, appealing aesthetics, and robust capabilities.

One of the standout features of the Apple II was its open architecture, which allowed users to expand and enhance the computer's functionality. This design enabled hundreds of third-party hardware and software developers to contribute to its ecosystem, resulting in an array of peripherals, including printers, modems, and storage devices. The Apple II utilized a MOS Technology 6502 microprocessor running at a clock speed of 1 MHz. Initially equipped with 4 KB of RAM, the machine could be expanded to 48 KB, accommodating more complex applications and programs.

The Apple II was also notable for its colorful graphics. It was one of the first computers to support color display, offering a 6-color palette with a resolution of 280x192 pixels in 16 colors when using its Color Graphics Card. This feature significantly enhanced the visual appeal of games and educational software developed for the platform, making computing more accessible and entertaining for various audiences.

Apple's commitment to user experience was evident in the design of the machine. It featured an integrated keyboard and a plastic case, which was both durable and visually appealing. The self-contained design included drive bays for floppy disk drives, allowing for quicker data access than traditional tape drives. It also supported audio output, enabling sound effects and music, a novelty at the time.

The introduction of the Apple DOS operating system further underscored the machine's capabilities. DOS streamlined file management and made it easier for users to navigate and manage their data. The combination of hardware and software positioned the Apple II as an educational tool and a gaming platform, fostering a vibrant software ecosystem.

The Apple II family continued to evolve, with variations like the Apple II+, IIe, and IIgs being introduced over the years. These iterations brought enhancements in memory, processing power, and graphics capabilities. The legacy of the Apple II endures, not only as a foundational product in personal computing but also as a symbol of innovation that paved the way for future advancements in technology. Its impact is still felt today, as it inspired countless developers and shaped the trajectory of the computer industry.