What does the "0x" in "0x2F" mean? I get that the "2F" is hexadecimal, but what relevance does the "0x" have?

 

0x means a hexadecimal number follows

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It is used to distinguish between 'AF' the alphabetic string and 0xAF the hexidecimal number. The number starts with a digit which has the same value in any number base.

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and 0b will often proceed binary numbers, just FYI

 

Hi,


In that little code example I sent you will see on the first line the code LIST P=18F2550,r=hex - radix=hex - meaning that any uncoded number will be treated as a hex value - so if you had movlw 16 it would be recognised as hex 0x16.

It is also quite popular for the radix=dec when 16 is simply that, but more commonly coded as .16 - the full point denoting a decimal value follows.

Even when using the Radix statement, to avoid problems its perhaps wise to always code your values accordingly 0xhex or .dec or binary b'01010101'

 

As many have said, the 0x (in many languages including C and PIC ASM) is a prefix added to hexadecimal numbers. 0b means binary and 0d usually designates decimal, although decimal is usually default and assumed to be decimal without any prefix. 0O (zero-oh) usually means octal :P

 

thanks a lot

 

If you read the MPASM/MPLAB help files, all these things are explained.

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I sometimes think a helpfile that lists all the help files and explains what kind of stuff they cover is in order.

 

If you want to figure out the binary/hexadecimal thing use this chart I created. I constantly use it when I'm writing code for PICs. It helps me speed up the coding after I create a chart of how I want ports to be either High or Low.


heres a little bit of sample code

0x0A means 00001010 in Binary which means Pins 1 and 3 are High and the rest are Low

Attached Files

Hex-Binary Chart.txt (26.2 KB, 18 views)

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Doesn't the Windows Calculator provide a simple mechanism for looking at a number as decimal, binary, or hex?

 

I wanted a quick reference guide I can use when I'm coding. All I have to do is do a search in my hex/binary chart and go straight to the correct hex code

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This is the way the world ends,
This is the way the world ends,
This is the way the world ends,
Not with a BANG
But with a BELCH

BURRRRRRRRRRPPPPPPP

 

I wrote a little free windows program that does dec/hex/binary conversion to 32bits and has ascii key codes displayed etc etc;

"HexCon" Hex-Decimal-Binary converter

 

The hex to bin and bin to hex should be engraved deeply into your brain if you want to work in embedded systems. Along the line of 2+3=5 type of recall. You need to know 1011 is B and 1101 is D without thinking.

The time it takes to learn the 16/32 conversion will be paid back to you many times.

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I'm just not sure why you made the chart go up to 2 digits of hex and 8 of binary. Hex converts in nice 4 bit chunks, thats why its used with computers. You can look at any hex digit and know what the corresponding block of 4 binary bits ("nibble") is without knowing the digits that proceed it. Conversly, if I tell you "I have a decimal number, the fifth digit is 9" you can't get the corresponding binary for that part of the number.