67 lines
3.2 KiB
Plaintext
67 lines
3.2 KiB
Plaintext
=== Display
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The orignal Apple ][s didn't come with a display. The user needed to use either a standard
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television or a monitor in order to see the computer's output. The EPPLE ][ emulates a variety of
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displays; you can cycle between the different types using +F2+.
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There are two major types of displays: televisions and monitors. Monitors generally have
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higher quality (sharper) displays. The displays show the normal visible area of the NTSC
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video signal generated by the emulated Apple ][ machine.
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==== Monitors
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The emulator provides a color monitor, and a green monochrome monitor.
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These emulate standard, no-frills NTSC monitors. The most noticeable characteristic of a monitor
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is the horizontal display of pixels. Monitors react faster than TVs, so two adjacent pixels will
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not merge together; both will be distinctly visible, with blackness between them. For example,
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type in the following Applesoft command, then cycle through the display types. The monitors
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will show thin, vertical, green lines; TVs will show continuous horizontal lines.
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--------
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GR : COLOR=4 : HLIN 10,20 AT 10
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--------
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==== Televisions
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Televisions react more slowly to
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changes in the incoming video signal than monitors do, and as a result, horizontal pixels will
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merge together, forming a more uniform appearance. EPPLE ]['s television mode emulates the
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signal decoding circuitry of a real television. This includes separating out the ``chroma'' portion
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of the incoming NTSC video signal using a filter algorithm, and _calculating_ the color to display.
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==== Scan Lines
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NTSC displays (TVs or monitors) usually receive signals that are interlaced. However, the
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Apple ][ doesn't generate interlaced screens. This causes blank rows between each displayed
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row of pixels. The EPPLE ][ emulates this behavior, but also allows you to ``fill in'' these
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black rows with a copy of the row above it, for a more continuous display (vertically). Use
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the F4 key to toggle between these two modes.
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==== Resolution
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The Apple ][s are commonly documented as having a resolution of 280x192 pixels, and to an
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extent this is true. Vertically there are 192 pixels, but since there is no interlacing,
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it is more accurate to display them with one blank space between each. So the EPPLE ][ has
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two times 192, or 384, vertical pixels in its display. Horizontally there are 280 pixels, but
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each could also be shifted right one-half dot, allowing for two times 280, or 560, different
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horizontal displayable positions. To emulate this, the EPPLE ][ shows each emulated pixel as
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two pixels wide, and displays an emulated half-dot shift as an actual one pixel shift. So the
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display area of the EPPLE ][ is 560x384. There is an informational area below and to the
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right of the emulated display that shows various statistics of the emulator. So the total screen
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area used by the EPPLE ][ is a standard 640x480 pixels.
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==== Full Screen
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The EPPLE ][ can run in either full-screen mode, or within a window. Use the +F3+ key to toggle
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between the two.
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==== Informational Area
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The area at the bottom and the right of the EPPLE ][ display show various information about
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the emulator.
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* POWER light
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* current cards in SLOTS
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* CASSETTE tape information
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* emulated CPU speed (MHz)
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* function-keys help
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