String

VN

DSP

NVA

DATA

DATA

Terminator

The SWEET 16 registers are as shown:

 

low

high

low

high

low

high

low

high

$0000

1E

00

08

08

08

0A

00

00

 

----------

----------

----------

----------

 

 

 

 

 

 

register

register

register

register

 

 

R0

 

R1

 

R2

 

R3

 

(acc)

(source)

(dest)

(#bytes)

The low order byte of R0, the SWEET 16 accumulator, has $1E in it, the last byte moved (the 8th).

The low order byte of the source register R1 started as $00 and was incremented eight times, once for each byte of moved data.

The high order byte of the destination register R2 contains $0A, which was entered at 10 (the variable) and poked into the SWEET 16 code. The low-order byte of R2 was incremented exactly like R1.

Finally, register R3, the register that stores the number of bytes to be moved, has been poked to 8 (the variable B) and decremented eight times as each byte got moved, ending up $0000.

By entering character strings and varying the number of bytes to be moved, the SWEET 16 registers can be observed and the contents predicted.

Working with this demonstration program, and study of the text material will enable you to write SWEET 16 programs that perform additional 16 bit manipulations. The unassigned opcodes mentioned in the "WOZ Dream Machine" article should present a most interesting opportunity to "play".

SWEET 16 as a language - or tool - opens a new direction to Apple ][ owners without spending a dime, and it's been there all the time.

"Apple-ites" who desire to learn machine language programming, can use SWEET 16 as a starting point. With this text material to use, and less opcodes to learn, a user can quickly be effective.

Listing #1

>List

10PRINT "[D]BLOAD SWEET": REM CTRL D

20CALL - 936: DIM A $ (10)

30INPUT "ENTER STRING A $ " , A $

Page 59
Image 59
Apple II manual Dsp, Print Dbload Sweet REM Ctrl D, Input Enter String a $ , a $, Nva

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.