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1 Using block files

Historically Forth was implemented on small computers as an operating system in its own right. Mass storage was not organized in files but as a sequence of 1 KB blocks. A block was addressed with a block number. This way a diskette drive provided a few hundred blocks and if you had a fixed disk you simply had thousands of those blocks.

Both program text and arbitrary data can be stored in blocks. In order to hold source text the 1K block is treated as 16 lines with 64 characters each. This is called a ‘screen’ sometimes.

When loading (i.e. interpreting) a block with source text it appears as a single line of 1024 characters. The only exception to this is the word \ (begin comment to end of line) which skips text up to the end of a line in a block.


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1.1 Blocks in files


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1.2 Words to handle blocks


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1.3 Words to load source from blocks


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1.4 Editing blocks


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