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Update apple2_hires.md

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## Summary
* [Introduction](#introduction)
* [Structure of the hires screen in RAM](#structure-of-the-hires-screen-in-ram)
* [Summary table of addresses in RAM](#summary-table-of-addresses-in-ram)
## Introduction
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## Structure of the hires screen in RAM
The Apple ]\[ has 2 hires pages. One in $2000-$3FFF. The second one in $4000-$5FFF. Each page is thus 8192 bytes long.
The dimensions of one hires page is 40 bytes wide and 192 lines high. 40x192 = 7680 bytes. 512 bytes are "missing" and in fact not used/displayed.
The dimensions of one hires page are 40 bytes wide and 192 lines high. 40x192 = 7680 bytes. 512 bytes are "missing" and in fact not used/displayed.
The hires screen is divided in 3 zones of 64 lines. Let's call it zones A.
Each section is then divided in 8 sub-sections of 8 lines. Let's call these zones B.