****PeterJohn BookKeeping Calculator; We Wanted Simple and Easy Calculator for BookKeeping. **We Needed Independent Memory, Grand Total Memory. **We Wanted AC, C, BackSpace, some of calculators doesNot have "C"(Clear Key), or some of calculators doesNot have "BackSpace" key. **We Wanted Not "MRC" But "MR" and "MC". some of calculators doesNot have the separated "MR" and "MC". "MRC" makes us confused, when we want "MR", if there's Only "MRC", we might Ms-touch "MC", when we want "MC", if there's Only "MRC", we might Mis-touch "MR". when we want "MR", just we want Not "MRC" but "MR". when we want "MC", just we want Not "MRC" but "MC". ****Basic Functions; We determined that we regard "CASIO ND-26S Professional Business Calculator", its keyboard layout and basic function as being the industry standard calculator 'cause it is Recommended by the "Japan Calculator Skills Certification Association" and by some of BookKeeping School. We implemented some of functions below; 01) Independent Memory Calculation(M+,M-,MR,MC); 2x3,M+→6 5x6,M+→30 8x9,M+→72 MR→108 MC 02) GrandTotal Memory Calculation(=,GT); 2x3,=→6 5x6,=→30 8x9,=→72 GT→108 03) Constant Calculation(++,--,xx,÷÷) AC 3++ 4=→7 5=→8 6=→9 AC 3-- 4=→1 5=→2 6=→3 AC 3xx 4=→12 5=→15 6=→18 AC 3÷÷ 4=→1.333 5=→1.666 6=→2 AC 04) Square Calculation(x=) 3x=→9 6x=→36 9x=→81 GT→126 05) SquareRoot Calculation(√) 4√→2 5√→2.236 06) Percent Calculation(%) 456%→4.56 07) Tax Rate Set and Tax Calculation; (TaxRateSet) AC,%,10,%→10 (TaxRate) AC,TAX+→10 AC,1000,TAX+→1,100 AC,1100,TAX-→1,000 "PeterJohn BookKeeping Calculator" is Created Using "PeterJohn" technology. So that you can use "Divide Water Keyboard" in LandScape mode. ****Warning About "Screen Rotation When Device Rotated" Settings; There are Only Three Options in "Settings"; 1) AutoRotation When Portrait Orientation is "UnLocked". If you use this app when Portrait Orientation is "UnLocked", you had better choose "1) AutoRotation". 2) LandScape When Portrait Orientation is "Locked". 3) PortRait When Portrait Orientation is "Locked". if you'd like to Fix "2) LandScape" or "3) PortRait", you had better "Portrait Orientation Lock". We don't recommend the Other Option; Choosing 2) LandScape or 3) PortRait When Portrait Orientation is "UnLocked".. Best Regards, --Yasushi Yassun Obata