7 The optional Block word set

( -- a-addr )

a-addr is the address of a cell containing zero or the number of the mass-storage block being interpreted. If BLK contains zero, the input source is not a block and can be identified by SOURCE-ID, if SOURCE-ID is available. An ambiguous condition exists if a program directly alters the contents of BLK.

7.3.2 Block buffer regions.

( u -- a-addr )

a-addr is the address of the first character of the block buffer assigned to mass-storage block u. An ambiguous condition exists if u is not an available block number.

If block u is already in a block buffer, a-addr is the address of that block buffer.

If block u is not already in memory and there is an unassigned block buffer, transfer block u from mass storage to an unassigned block buffer. a-addr is the address of that block buffer.

If block u is not already in memory and there are no unassigned block buffers, unassign a block buffer. If the block in that buffer has been UPDATEd, transfer the block to mass storage and transfer block u from mass storage into that buffer. a-addr is the address of that block buffer.

At the conclusion of the operation, the block buffer pointed to by a-addr is the current block buffer and is assigned to u.

( u -- a-addr )

a-addr is the address of the first character of the block buffer assigned to block u. The contents of the block are unspecified. An ambiguous condition exists if u is not an available block number.

If block u is already in a block buffer, a-addr is the address of that block buffer.

If block u is not already in memory and there is an unassigned buffer, a-addr is the address of that block buffer.

If block u is not already in memory and there are no unassigned block buffers, unassign a block buffer. If the block in that buffer has been UPDATEd, transfer the block to mass storage. a-addr is the address of that block buffer.

At the conclusion of the operation, the block buffer pointed to by a-addr is the current block buffer and is assigned to u.

7.6.1.0800 BLOCK.

Extend the semantics of 6.1.1360 EVALUATE to include: Store zero in BLK.

( -- )

Perform the function of SAVE-BUFFERS, then unassign all block buffers.

( i×x u -- j×x )

Save the current input-source specification. Store u in BLK (thus making block u the input source and setting the input buffer to encompass its contents), set >IN to zero, and interpret. When the parse area is exhausted, restore the prior input source specification. Other stack effects are due to the words LOADed.

An ambiguous condition exists if u is zero or is not a valid block number.

3.4 The Forth text interpreter.

( -- )

Transfer the contents of each UPDATEd block buffer to mass storage. Mark all buffers as unmodified.

( -- )

Mark the current block buffer as modified. An ambiguous condition exists if there is no current block buffer.

UPDATE does not immediately cause I/O.

7.6.1.0800 BLOCK, 7.6.1.0820 BUFFER, 7.6.1.1559 FLUSH,
7.6.1.2180 SAVE-BUFFERS.

( -- )

Unassign all block buffers. Do not transfer the contents of any UPDATEd block buffer to mass storage.

7.6.1.0800 BLOCK.

( u -- )

Display block u in an implementation-defined format. Store u in SCR.

7.6.1.0800 BLOCK.

( -- flag )

Extend the execution semantics of 6.2.2125 REFILL with the following:

When the input source is a block, make the next block the input source and current input buffer by adding one to the value of BLK and setting >IN to zero. Return true if the new value of BLK is a valid block number, otherwise false.

6.2.2125 REFILL, 11.6.2.2125 REFILL.

( -- a-addr )

a-addr is the address of a cell containing the block number of the block most recently LISTed.

A.7.6.2.2190 SCR.

( i×x u₁ u₂ -- j×x )

LOAD the mass storage blocks numbered u₁ through u₂ in sequence. Other stack effects are due to the words LOADed.

Extend the semantics of 6.2.2535 \ to be:

Perform the execution semantics given below.

( "ccc<eol>" -- )

If BLK contains zero, parse and discard the remainder of the parse area; otherwise parse and discard the portion of the parse area corresponding to the remainder of the current line. \ is an immediate word.