Apple II manual

MD2 subroutine (address $F4E2)

Purpose: To clear the 3-byte MANT1 field for FMUL and FDIV, check for inital result exponent overflow (and underflow), and initialize the X-REG to $17 for loop counting.

Entry: the X-REG is cleared by the user since it is placed in the 3 bytes of MANT1. The A-REG contains the result of an exponent addition (FMUL) or subtraction (FDIV). The carry and sign status bits should be set according to this addition or subtraction for overflow and underflow determination.

Exit: The 3 bytes of M1 are cleared (or all set to the contents of the X-REG on Entry) and the Y-REG is loaded with $17. The sign bit of the A-REG is complemented and a copy of the A-REG is stored in X1. FP2, SIGN, SCR, and the X-REG are not disturbed.

Uses: NORM.

Caution: Exponent overflow results in an exit to location $3F5. Exponent underflow results in an early return from the calling subroutine (FDIV or FMUL) with a floating point zero in FP1. Because MD2 pops a return address off the stack, it may only be called by another subroutine.

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.