Section 4: Programming 272

Programming Label D : Months for Savings to Overtake Downpayment

Instead of calculating monthly a sequence like before, the task here is to calculate a specific answer—the month at which sayings are great enough to permit purchase of the house. We will set up a counter for the number of months in R8 and use a logical test (x>y, i.e., downpayment>savings) to decide if we should continue for another month or if the increased savings has overtaken the required downpayment.
1. Switch to W/PRGM. Do not press fPRGM.
2. See 84, the code for R/S. Since R/S was not the last instruction in LBL C, press SST, see 22, the code for GTO.
3. Now press SST, see 00, the code for 0. You are now at the end of the previous segment of the program and are ready to key in the sequence below.
 
KEY
ENTRY
CODE
SHOWN
COMMENTS
LBL 23  
D 14  
RCL 1 34 01  
STO 2 33 02 Reset savings and
RCL 4 34 04 dnpmt
STO 5 33 05  
0 00 Start month zero
STO 8 33 08  
LBL 23  
1 01 Return point
1 01  
STO 33 Add one to month
+ 61 counter
8 08  
B 12 Calculate savings
A 11 Calculate dnpmt
g x>y 35 24 If savings less
GTO 22 than dnpmt return
1 01 to LBL 1, otherwise
RCL 8 34 08 recall month
RTN 24