_____ _____ _____ _____

X1 M1

NORM1 subroutine (address $F455)

Purpose: To normalize a floating point value in FP1 when it is known the exponent is not -128 (X1=0) upon entry.

Entry: An unnormalized number is in FP1. The exponent byte should not be 0 for normal use.

Exit: The normalized value is in FP1. E, FP2, SIGN, and SCR are not not disturbed. The A-REG is altered but the X- and Y-REGs are not.

ADD Subroutine (address $F425)

Purpose: To add the two mantissas (M1 and M2) as 3-byte integers.

Entry: Two mantissas are in M1 (through M1+2) and M2 (through M2+2). They should be aligned, that is with identical exponents, for use in the FADD and FSUB subroutines.

Exit: the 24-bit integer sum is in M1 (high-order byte in M1, low-order byte in M1+2). FP2, X1, E, SIGN and SCR are not disturbed. The A-REG contains the high-order byte of the sum, the X-REG contains $FF and the Y-REG is not altered. The carry is the '25th' sum bit.

Example: FP1 contains +5 and FP2 contains +7 prior to calling ADD.

 

_____

 

_____

 

_____

 

 

_____

 

 

 

 

 

 

 

FP1:

$82

$50

0

0

(+5)

_____

_____

_____

_____

 

 

X1

 

 

M1

 

 

 

 

 

 

 

 

 

_____

 

_____

 

_____

 

 

_____

 

 

 

 

 

 

 

FP2:

$82

$70

0

0

(+7)

_____

_____

_____

_____

 

Upon exit, M1 contains the overflow value for +12. Note that the sign bit is incorrect. This is taken care of with a call to the right shift routine.

 

_____

 

_____

 

_____

 

_____

 

 

FP:

$82

$C0

0

0

(+12)

_____

_____

_____

_____

 

 

 

 

 

 

 

 

 

 

Page 77
Image 77
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.