here that if you're not using *Layer 2*, the banks it occupies CAN be used for other purposes including machine code programs. They just cannot be released. Banks marked as *in-use*, remain reserved after a **NEW** command and are only released at a reset (or with this **BANK** *n* **CLEAR**). **BANK CLEAR** reports **A Invalid Argument, 0:1** if you try to clear banks **1**,**3**,**4** and **6** even if you have given the **BANK 1346 USR** command which is described below. *NextZXOS* allocates 64K to the RAMdisk by reserving banks **1**,**3**,**4** and **6**; **BANK 1346 USR** allows you to release these for use by your programs. Once you give the command: ``` BANK 1346 USR ``` the following things happen; first all files in the RAMdisk are deleted, then the drive itself is unmounted and using **BANK** commands on these banks stops producing errors. To undo this action and reinstate the RAMdisk you will need to use: ``` BANK 1346 FORMAT ``` which will erase the contents of these banks and re-attach them to the RAMdisk. The disk itself however will need to be manually mounted again by using the **MOVE...IN** command. See *Chapter 19 for details.* Bank contents can be copied and erased in whole or in part using the **BANK COPY** and **BANK ERASE** commands.There's also a specific one that copies data quickly to and from the screen but we'll look at that separately. The syntax to copy bank data is: **BANK** *source_bank* **COPY** [*source_offset, len*] **TO** *destination_bank [,dest_offset*] where *source_bank* is a readable bank number to copy *from* while *destination_bank* is a writeable bank number. *Source_offset* and *len* signify the location within the source bank and the size *in bytes* of the memory chunk we're copying. If the latter are specified, then the *dest_offset* must also be specified. Let's try: ``` BANK 9 COPY TO 47 ``` will copy the bank holding the first third of *Layer 2* into bank **47** while, ``` BANK 1 COPY TO 47 ``` will return **A Invalid argument**, unless **BANK 1346 USR** has been used! ``` BANK 9 COPY 8192, 8192 TO 47, 0 ``` will copy the bottom half of the first third of the *Layer 2* screen to the start of bank **47** (Once you untangle that tongue-twister you can see how this can create interesting blinds effects!). It's also quite handy to quickly erase the whole or part of a bank (fill it with zeroes or an arbitrary byte value). This is accomplished by the **BANK ERASE** command whose syntax is: **BANK** *n* **ERASE** *[offset, len][,][value]* where *n* is the number of writeable bank, *offset* is the optional starting point of the erase and *len* is the length (in bytes) of the area to be erased. The optional *value* will fill the area with a byte of your choosing or – if omitted – **00h**. Here are some examples using *Layer 2* and an image present in your **System/Next™** distribution (you will need to provide the image in 256 x 192 x 256 colour BMP format): ``` 10 CD "ENTER HERE THE FOLDER" 20 LAYER 2,1 30 .bmpload yourfile.bmp ```