Registers
Summary of Storage Registers
Storage Registers:
 As previously stated there are 21 storage registers R0-R9,
 R.0-R.9, and I the index register.  The STOre key (4,4)is used to
 copy the value in X into any of these 21 registers and the ReCaLl
 Key (4,5) returns to X the value stored in any of these
 registers.  To address R0-R9 click STO or RCL followed by 0-9.
 To address R.0 to R.9, click STO or RCL followed by . followed by
 0-9.  The index register I is addressed by clicking STO (4,4) or
 RCL (4,5) followed by I (4,2 2,5) or (2,5) as the f is optional
 and is assumed if omitted.

Storage Register Arithmetic:
 It is also possible to use the contents of X to perform
 arithmetic on the contents of R0-R9 by clicking STO (4,4)
 followed by one of the 4 basic arithmetic functions ( x - +)
 (1,0 2,0 3,0 4,0) then followed by 0-9 to indicate the target
 storage register.  For example to divide the value in R6 by the
 current value of X, click STO  6 (4,4 4,0 2,9).

Indirect Register Access:
 The index register I can be used as a storage register or it can
 be used as an indirect pointer to R0-R9 or R.0-R.9.  If the
 absolute value of the integer part of I is 0 to 9, it points to
 R0 to R9.  If the absolute value of its integer part is 10 to 19,
 it points to R.0 to R.9.  Clicking STO (4,4) or RCL (4,5)
 followed by (i) (4,2 2,4) or (2,4)(the f key is assumed if
 omitted), either copies X into the register pointed to by I or
 recalls to X the value in the register pointed to by I. For
 example if I contents 5.67 and R5 contains 34.56 then clicking
 RCL (i) (4,5 4,2 2,5) will return to X the value 34.45.

 Indirect storage register arithmetic can be performed using (i)
 instead of 0-9 as noted above.  While direct storage register
 arithmetic can only be performed on R0-R9, indirect storage
 register arithmetic can address all 20 storage registers.  If the
 absolute value of the integer part of I is greater than 19 an
 error will occur if an indirect operation is attempted.

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