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Windows[TM] endowed its built-in dialog box pushbuttons with a nice 3-D look -- they appear to press in when you click on them with the left mouse button or with […]

When an X-Window application (or client) begins executing, it specifies one or more fonts that will be used by the application. It is the responsibility of the X server to […]

Microsoft Windows 3.0 provides a rich set of objects and primitives for dialog boxes. The basic, predefined control classes are flexible and well developed, allowing a great deal of freedom […]

It is possible to draw on a bit mapped display using the Commodore 64 home computer. Instructions are given on how to do this, and how to draw lines in machine language routines. Two program listings are given, one in BASIC and one in machine language. Both are drawing routines.

Bit-mapped graphics are a method of display on a high-resolution screen that involves using eight bytes for each character displayed. The program tells how to turn on individual pixels on the screen. Instructions are given on how to use the program, which is for the Commodore 64. A complete program listing is included.

Text and graphics can be displayed simultaneously without sacrificing system price or performance by designing a CRT controller (CRTC)-based graphic-display-block (GDB) system. The system involves creating GDBs or bit-mapped graphics windows within the text. The GDBs are integrated into the normal CRTC display lists and can be displayed without extra hardware. The AM8052 CRTC chip is a general-purpose CRTC for raster-scan displays that can be used in a GDB system. The article includes a block diagram showing the architecture of a GDB system, circuit diagrams to illustrate the operation of a GDB system, and a diagram for a dynamic RAM-based GDB- implementation scheme.

Custom character graphics can provide smoother animation, but may prove difficult to program. Character graphics and bit-mapped graphics are discussed, with advantages and disadvantages of each. Instructions are given on how Atari characters are formed and how to develop custom characters. Graphs are included to show resolution, memory needed and colors available for Atari graphics. A custom character example is shown. Full program listings are included.

Commodore 64 computers can have screen resolutions of up to 320 by 200 individually addressable pixels. There is not enough RAM to assign one byte per pixel, so one bit is assigned per pixel in a selected area of memory. The user should have an understanding of the binary number system and logical operators to manipulate these bits. This technique is called bit mapping. A graphics program listing is included to illustrate bit mapping on the 64.

A tutorial is presented to explain how to vary the screen size of the VIC-20 computer. Screen character codes and screen memory maps are listed in tables. Two graphics programs illustrate screen size applications and bit-mapping of the screen.