BSAVE (bitmap format)

A BSAVE Image (aka "BSAVED Image") as it is referenced in a graphics program is an image file format created usually by saving raw video memory to disk (sometimes but not always in a BASIC program using the BSAVE command).

The BASIC BSAVE command is a general command meant for dumping ranges of memory addresses to disk. Data could be recalled using the counterpart BLOAD command. Some platforms provided a BRUN command that would immediately attempt to execute the loaded RAM image as a program.

BSAVE was in general use as a file format when the IBM PC was introduced. It was also in general use on the Apple II in the same time period. Although the commands were available on the Commodore PET line, they were removed from the later (and more popular) Commodore 64 and VIC-20 computers. In 1985 the Commodore 128 was released with Commodore BASIC version 7.0 which restored the BSAVE and BLOAD commands.

The BSAVED format is a device-dependent raster image format; the file header stores information about the display hardware address, and the size of the graphics data. The graphics data follows the header directly and is stored as raw data in the format of the native adapter's addressable memory.

There is no file compression, and therefore these load very quickly and without much programming when displayed in native mode.

No additional information, such as screen resolution, color depth and palette information, bit planes and so on, is stored. Video adapters were simple when this format was in wide use and the other information necessary to display the image could usually be inferred by programs that loaded such files.

The BASIC programming language was shipped as part of the operating system on the first IBM PCs, Apple and Commodore 8-bit (like Commodore 64/128) computers. On computers that did not start up in BASIC, BASIC was loaded by manually running the BASIC interpreter. The user could then type BASIC commands in direct mode or by creating and/or running a numbered BASIC program within the interpreter.

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