Converting a 32 bits word to decimal

DutchGuy · 1. September 2020

For a game I'm making I want to put the score in the game on the screen. I can already put numbers on the screen by calling my routine JSR PutA_XY. A is value 0 to 9 and XY are the screen coordinates.

I thought I could look up and find a standard routine that converts $FFFF to 65535 and $0000 to 00000 (and all between) but I could not find one.

What I can remember from the past is that you should count how many times you can subtract 10000, 1000, 100, 10 and 1 from the starting number.
But as said if someone has this code or a link to it, it would save some time programming and debugging

Freak · 1. September 2020

It is maybe easier to use the decimal mode for the score to avoid converting numbers.

With decimal mode you simply print the nibbles as your digits. If you set the Decimal Flag in the Status-Register before adding, the result will look as this example: $09 + $01 = $10

Cheers,

Thomas

Hoogo · 1. September 2020

In case you're already quite fit in Assembler:

You could look at the 16/24 bit divisions and change them into something that divides 32 Bit by 8 Bits.

Every remainder is one digit.

JeeK · 1. September 2020

For my directory routine without BASIC interpreter routines I developed a binary to string routine based on BCD conversion.

See explanation inline ...

Code

;--------------------------------------------
; 16 bit binary printed as 4 digit ASCII string
; print left-aligned without leading zeros
H = $FB
BOUT = $FFD2
INT2ASCII
STA H ; high Byte
LDX #2 ; 3 bytes
LDA #$00
LOOP4 STA BUF,X ; clear BCD buffer
DEX
BPL LOOP4
SED ; decimal mode
LDX #16 ; bit counter
LOOP5 ASL L ; 16 bit value times 2
ROL H ; keep carry
LDY #$02 ; 3 BCD bytes (6 digits)
LOOP6 LDA BUF,Y ; BCD value times 2
ADC BUF,Y
STA BUF,Y
DEY ; BCD byte counter
BPL LOOP6
DEX ; all binary bits processed?
BNE LOOP5
CLD ; end decimal mode
LDY #$00 ; index, beginning from most-significant bit
STY H ; flag indicating not-zero character
LOOP7 LDA BUF,Y ; BCD buffer
PHA
LSR
LSR
LSR
LSR ; higher nibble
JSR LEADER ; leading zeros to spaces
PLA ; BCD buffer
AND #$0F ; lower nibble
JSR LEADER ; leading zeros to spaces
INY ; next BCD byte
CPY #$03 ; all BCD bytes processed?
BNE LOOP7
LDA H ; only zero digits?
BNE EXIT ; RTS from LEADER routine!
; if value was zero, output "0"
ZOUT ORA #$30 ; to ASCII digit
JMP BOUT ; print digit, if value = 0
;--------------------------------------------
LEADER
BNE NOT0 ; not zero
CMP H ; leading digit 0?
BNE ZOUT ; zero digit, but not a leading one
EXIT RTS ; ignore a leading "0"
;--------------------------------------------
NOT0 STA H ; memorize a digit different from "0"
BNE ZOUT ; print it and go back
;--------------------------------------------
BUF !BY 0,0,0 ; BCD value buffer

Alles anzeigen

Neptun · 1. September 2020

Code

ldx lb
lda hb
jsr $bdcd

Mac Bacon · 1. September 2020

Another possibility is the double dabble algorithm.

Endurion · 2. September 2020

Alternatively simple do not store the score as binary, but each digit separately. Ideally on screen. For 6 or more digits I usually only keep the score in the display and update it in place there.

Nitpick: $ffff is 16 bit, not 32bit

enthusi · 2. September 2020

In general it is a good idea to take a deeper look at this codebase (another algo was linked from it before):
https://codebase64.org/doku.ph…mal_to_decimal_conversion

DutchGuy · 2. September 2020

Everybody thank for the reply, it really helped.

Endurion ok, that is what I'am doing at the moment. It works ok but iI am wondering what I am going to do if I want to compare the score with the high-score or want to add bonus point at the end of a level.

Do you than convert it to HEX or do you keep calculating in the decimal form as it is in memory?

Mac Bacon · 2. September 2020

Zitat von DutchGuy

iI am wondering what I am going to do if I want to compare the score with the high-score

Just keep the high score in screencodes as well.

JeeK · 5. September 2020

Zitat von DutchGuy

I am wondering what I am going to do if I want to compare the score with the high-score or want to add bonus point at the end of a level.

Do you than convert it to HEX or do you keep calculating in the decimal form as it is in memory?

High-Scores, I think that's what Mac Bacon has meant, could be compared like strings. Assuming the score values have all the same length, just walk through position 0 to length-1 (from higher significant to lower significant digits) of the score string and skip as long the values are equal, otherwise the decision is derived from last compare.

For adding some bonus value take the score value as BCD value (probably transformable on the fly) and add the bonus as BCD value in decimal mode and transform it back to screen codes.

DutchGuy 1. September 2020