Routines 
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Used by the routine at PRINT_FP.
This subroutine calculates the approximate number of digits before the decimal in x, the number to be printed, or, if there are no digits before the decimal, then the approximate number of leading zeros after the decimal. It is entered with the A register containing e', the true exponent of x, or e'2, and calculates z=log to the base 10 of (2↑A). It then sets A equal to ABS INT (z+0.5), as required, using FP_TO_A for this purpose.


LOG_2_A  2DC1  LD D,A  The integer A is stacked, either as 00 00 A 00 00 (for positive A) or as 00 FF A FF 00 (for negative A).  
2DC2  RLA  
2DC3  SBC A,A  
2DC4  LD E,A  These bytes are first loaded into A, E, D, C, B and then STK_STORE is called to put the number on the calculator stack.  
2DC5  LD C,A  
2DC6  XOR A  
2DC7  LD B,A  
2DC8  CALL STK_STORE  
2DCB  RST $28  The calculator is used.  
2DCC  DEFB $34  stk_data: log 2 to the base 10 is now stacked  
2DCD  DEFB $EF,$1A,$20,$9A,$85  
2DD2  DEFB $04  multiply: A*log 2 i.e. log (2↑A)  
2DD3  DEFB $27  int: INT log (2↑A)  
2DD4  DEFB $38  end_calc  
The subroutine continues into FP_TO_A to complete the calculation.

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