Description: Apple II and II+: Memory typically available to users
Header: Apple II and II+: Memory typically available to users


 After startup, Applesoft's FRE(0) statement reports the same amount, 48K, of
 free memory in the II Plus, the Apple IIe with 64K, and the Apple IIe or IIc
 with 128K.  No matter how much the maximum memory of the CPU is, you will never
 have more than 48K of memory available to you, since the microprocessor lets
 BASIC have DIRECT access to only 48K in Apple II family computers with memory
 configurations equal to or greater than 48K.

 This discrepancy stems both from the microprocessor's memory limit and from the
 demand placed on the system by the software. The Apple's 6502 microprocessor
 can directly access only 64K of memory (address 65536 ($FFFF)). Some of the 64K
 has to be loaded with system software: the monitor, Applesoft, I/O, stacks,
 keyboard, vectors, and text display.  The Apple's system monitor and Applesoft
 language routines reside in upper memory from $D000 to $FFFF. I/O ROM locations
 span from $C000 to $CFFF.  Finally, the system uses $0000 to $07FF for its
 stack, keyboard input, system vectors and text display.  This amount of
 software leaves you with 47103 bytes (the memory space between $0800 and $BFFF)
 that you can directly access through BASIC.

 The user can then decide to give more of this memory to an operating system and
 high resolution graphics.  For example, if you use DOS 3.3, you relinquish
 approximately 10.5K, the memory space from $9600 to $BFFF.  Similarly, high
 resolution graphics page 1 or 2 takes another 8K for each page.

 --> Adding more memory for the user

 Adding memory allows you to load operating systems not dependent on BASIC; it
 also lets you take advantage of the full 64K from assembly language programs. 
	Apple II and II+ users can add 16K to a 48K configuration if they install a
 RAM card in slot #0.

 In the IIe, this 16K "RAM card" is built onto the motherboard and is addressed
 in the same way as the card in the II and II+; that's why there's no slot #0 on
 the Apple IIe.  This additional 16K actually overlays the upper 16K of memory
 only by bank-switching between the ROM and RAM.
 Apple Technical Communications


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