Abstract
This chapter introduced the reader to the joys and sorrows of the C64 original OS and its BASIC programming language, including a foundational knowledge of sprites and sound programming via the VIC-II and SID chips respectively.
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- 1.
See Appendix C for a comprehensive list of each VIC-II register, its memory location and purpose.
- 2.
A particularly attentive reader may have noticed that, while the C64 has a standard screen resolution of 320 × 200 pixels, for storing a sprite’s X coordinate we are only using a specific memory location worth 1 byte of memory, i.e. 8 bits, which can cover values from 0 to 255 only! How do we place a sprite having a X coordinate between 256 and 320 then? Indeed, for each sprite, a 9th bit is needed to represent such values and it is stored in location 53264 ($D010) where each one of its 8 bits, from 0 to 7, is being assigned to the corresponding sprite.
- 3.
Comments in MS Basic could be added by using a REM statement. Using a colon instead allowed for concatenating two or more instructions on the same line.
- 4.
Note that, to keep the overall program more tidy and readable, we are inserting the new lines before the data block by numbering them accordingly.
- 5.
Check Appendix B for a list of emulators and other programming tools.
- 6.
For placing sprites in specific positions, we must be aware that, while the inner C64 display window is 320 × 200 pixels as discussed, sprites can also be placed also under the external borders, making the overall area for sprite movement 368 × 255 pixels. Location (0, 0) then is not at the upper left corner of the 320 × 200 window as we might have expected, but at the top left of the outside border.
- 7.
See Appendix D for a reference.
- 8.
The second nybble is used to enable filtering.
- 9.
See Appendix D for the different correspondences between numerical values and timings.
- 10.
A better implementation of CP/M was later built in the Commodore 128. This didn't help the new computer either, though, since, by that time, CP/M was past its prime and MS-DOS was rapidly becoming the leading business OS.
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© 2015 Springer Science+Business Media Singapore
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Dillon, R. (2015). Ready. In: Ready. Springer, Singapore. https://doi.org/10.1007/978-981-287-341-5_3
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DOI: https://doi.org/10.1007/978-981-287-341-5_3
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