The Museum of HP Calculators

HEX-DEC / DEC-HEX for the HP-33E

This program is by Glenn Hayhurst and is used here by permission.

This program is supplied without representation or warranty of any kind. Glenn Hayhurst and The Museum of HP Calculators therefore assume no responsibility and shall have no liability, consequential or otherwise, of any kind arising from the use of this program material or any part thereof.

Overview

This is a program that I wrote around 1978 that I used to convert DECIMAL numbers to HEX numbers when I worked for a company that made mainframe tape drives. One of my manufacturing jobs was to use a wirewrap gun to code the serial number into the backplane of the tape drives in HEX. I had to convert the decimal serial number that was stamped on the frame to a HEX value and then install the wires in the correct places bit by bit. after I wrote the first part of the program I had enough program steps left to write the reverse conversion from HEX to DECIMAL. It all fit within the 49 step limit of the HP-33E.

This program will convert DECIMAL numbers in the range of 0-65535 to their HEX equivalents.

It will also convert HEX numbers in the range of 0-FFFF to their DECIMAL equivalents.

Listing

Key        Display

_______________

ENTER↑  01-31
RCL 5   02-24 5
÷       03-71
g INT   04-32
STO 1   05-23 1
RCL 5   06-24 5
×       07-61
-       08-41
ENTER↑  09-31
ENTER↑  10-31
RCL 6   11-24 6
÷       12-71
g INT   13-15 32
STO 2   14-23 2
RCL 6   15-24 6
×       16-61
-       17-41
ENTER↑  18-31
ENTER↑  19-31
RCL 7   20-24 7
÷       21-71
g INT   22-15 32
STO 3   23-23 3
RCL 7   24-24 7
×       25-61
-       26-41
g INT   27-15 32
STO 0   28-23 0
RCL 1   29-24 1
f PAUSE 30-14 74
RCL 2   31-24 2
f PAUSE 32-14 74
RCL 3   33-24 3
f PAUSE 34-14 74
RCL 0   35-24 0
GTO 00  36-13 00
RCL 1   37-24 1   ← Entry point for H→D conversion
RCL 5   38-24 5
×       39-61
STO + 0 40-23 51 0
RCL 2   41-24 2
RCL 6   42-24 6
×       43-61
STO + 0 44-23 51 0
RCL 3   45-24 3
RCL 7   46-24 7
×       47-61
STO + 0 48-23 51 0
RCL 0   49-24 0

Enter the program, then store these three values that are used in the calculations.


4096    STO 5
256     STO 6
16      STO 7

Before running the program for the first time, hit g RTN. This sets the program to step 00.


Example:

To convert from DECIMAL to HEX:

        43961   ENTER↑  (stores value in Y register)
        R/S             (run program)

The display will pause with four numbers. These numbers appear in the order of the hex value. (See number conversion table below)


        10      11      11      9       (Display shows)
        A       B       B       9       (Hex Value)

Example: To convert from HEX to DECIMAL: Store the hex values in the following registers.

I.E.    (   HEX   )     A       B       B       9
        (DEC equiv)     10      11      11      9


        10      STO 1
        11      STO 2
        11      STO 3
        9       STO 0

Then:   GSB 37  (entry point for H→D conversion)

The program will run converting the values stored in registers 1, 2, 3, 0 to a decimal value that is left in the X register (display).


        Answer: 43961



Number conversion table:

HEX     DECIMAL
---     -------
0       0
1       1
2       2
...     ...
9       9
A       10
B       11
C       12
D       13
E       14
F       15

Registers used:

R0      HEX digit
R1      HEX digit
R2      HEX digit
R3      HEX digit
R4      unused
R5      4096    fixed value for program
R6      256     fixed value for program
R7        16    fixed value for program

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