Introducing The Bank Manager; Using The Second 64K Of Memory; Using The Bank Manager For Screen Images - AMSTRAD cpc 6128 User Instruction

Part 11: Introducing the Bank
Manager ....
Using the second 641{ of memory
The CPC6128 contains 128K of RAM (Random Access Memory) in two lots of64K.
CPIM Plus uses the fu11128K all the time, but BASIC does not normally use the
second 64K - orily the available memory in the first 64K. It would be a pity to leave
the extra 64K completely unused when programming in BASIC, so a program has
been provided to make special use of this extra memory. The program offers some
extra commands that make it possible to use the second 64K of RAM as either a
storage space for screen images, or as a storage space for strings.
The program providing these extra commands is known as the 'BANK MANAGER'
where 'bank' is a technical term used to describe a section of memory.
Using the BANK MANAGER for screen images
The 6128 is displaying a screen image all the time. To do this, it requires 16K of
memory in which to store the information about the colour and brightness of every
pixel (dot) on the screen. The 6128's memory allows up to six screen images (each in a
16K block) to be present in the computer's memory at anyone time. The BANK
MANAGER provides the facilities for you to juggle and display up to five of the six
possible screens from BASIC.
When you first switch on, the screen is displayed from a 16K block of memory (which
we will call 'Block 1') out of the first 64K. The other four screens are held in the second
64K of memory and are called Block 2, Block 3, Block 4, and Block 5.
Only Block 1 (from the first 64K) can be used to actually display a screen. Therefore,
to see a screen stored in the second 64K (Blocks 2 to 5), it is necessary to move the
required screen into Block
1.
The BANK MANAGER provides all the commands
needed to move screens around, such as I S eRE E NCO P Y which simply transfers one
screen to another, overwriting the contents of the existing screen; and
IS eRE ENS WA P which exchanges the contents of two screens.
Like the AMSDOS commands introduced earlier in this chapter, the BANK
MANAGER uses 'external commands' which start with the bar symbol
I
(obtained
by typing
[SHIFn@).
Chapter 1 Page 84 Foundation Course