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The symbol '$'???

viktornet
viktornet asked
on
Medium Priority
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Last Modified: 2010-04-04
Hello all, How are y'all doin'? OK...Here is my question...

1)Can anyone explain what the symbol $ means, and how is it used...

For example I have a declaration like this:
var TempByte : Byte;
begin
  TempByte := $80;
...
end;
2)Can you tell me how to determine what's the value of that, and if there are any other
ways to use this symbol what are they?

Viktor Ivanov
Comment
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Commented:
'$' indicates a hexadecimal numeral, and it also be used in the compiler directive.
for example, {$R *.dfm}

Author

Commented:
OK tell me something more specific, for example what number is represented by the value $80... I tried this to find out... Edit1.text := IntToStr($80);...but I'm not sure if that's the right value..
And why use hexadecimal instead of a decimal value like 128 or somethin' else... Can you tell me something more specific and I will accept your answer...Thanx..

Viktor Ivanov
Commented:
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Author

Commented:
OK, I'll give you the points... :-), even though I'm still not sure at least you tried, thanx...

Author

Commented:
OK, I'll give you the points... :-), even though I'm still not sure at least you tried, thanx...

Commented:
Hi,
Just a comment for clarification:
Hexadecimal numbers use 16 as a base while "normal" decimal numbers use 10. These are commonly used by programmers since they are easily converted to/from binary numbers used by the hardware.
Binary "digits" are: 0,1
Decimal "digits" are: 0,1,2,3,4,5,6,7,8,9
Hexadecimal "digits" are: 0,1,2,3,4,5,6,7,8,9,a,b,c,d,e,f

That makes:
Dec: - Hex:
  0 -   0
  1 -   1
  2 -   2
  3 -   3
.
  8 -   8
  9 -   9
 10 -   a
 11 -   b
 12 -   c
 13 -   d
 14 -   e
 15 -   f
 16 -  10
 17 -  11
.
 31 -  1e
 32 -  20
.
255 -  ff
256 - 100

Bin: - Hex:

00000001 - 01
00000010 - 02
00000011 - 03
00001111 - 0f
00010000 - 10

(do you see the 4:1 connection?)

In Pascal (Delphi) the compiler has to know when the programmer is using decimal representation of the numbers and when he/she uses hexadecimal representation. To do this, the hexadecimal numbers are prefixed with "$". In C/C++ the equivalent is "0x":

Pascal (Delphi):  "$fe"
C/C++          :  "0xfe"

As Buboi is mentioning, the "$" also represents a compiler directive. These have nothing to do with the hexadecimal representation.

A tip: To convert hexadecimal numbers to and from strings use:
  MyHexStr := IntToHex( 254, 2 ); // 254 => 'fe'
  MyInt := StrToInt( '$' + MyHexStr ); // MyHexStr = 'fe' => 254

Hope this doesn't make things worse, but simplify the matter to you.

/// John

Author

Commented:
Oh, hello! I seem to have forgotten to check the box and haven't recieved the message. Thanks a lot, and that's exactly what I was looking for. Thanks John. I've got a question. Ok let's say I've got 134. without using any calcs, or programming what do you need to do in order to convert the decimal value to hexadecimal. I think first I need to convert it to a binary and then get it's value into hexadecimal. Is that the way it is done or am I missing something? Thanx again. If I hadn't accepted the answer I would've given the points to you.

Regards,
Viktor Ivanov
i just don't believe this.

vik - pleez tell me that u're takin' the mickey outta us!

Black Death.

Author

Commented:
What???

Never mind, forget it....

Author

Commented:
I ain't taking the mickey outta anyone! if you wanna get points just tell me and I'll be happy to give you some... Alright ...

heey vik.
calm down.
u know i ain't hot 4 points.
(i never answered a q, just commented)

what i meant is:
was that a real q, or just a joke?

i didn't mean 2 attack u - 4 heaven's sake!

very sorry if u got that wrong.

Black Death.

Author

Commented:
It was a question some time ago, but I couldn't get an answer so accepted that guys answer. Anyway, John answered everythin' I needed to know, so I'm really thankful... just didn't get a small part of it, but anyway...who cares..  Talk to ya later

//Vik
ok.
i'm afraid i must have sounded stuck-up 2 ya.
sorry again.

til later & have a nice day,

Black Death.
ok.
i'm afraid i must have sounded stuck-up 2 ya.
sorry again.

til later & have a nice day,

Black Death.

Author

Commented:
Thanx . U 2

Regards,
Viktor Ivanov

Commented:
Hi Viktor,
What is it you really lack from my comment?
In the processor there is no difference between a decimal and a hexadecimal number since all is done binary.

If you want to convert 134 to hex "by hand", then do this:

1. Divide number by 16:
  134 / 16 => 8.375
2. Take fractional part of the answer times 16 to get first number.
This is called MODULO (134 mod 16):
  0.375 * 16 => 6 (put this farthest to the right)
3. Repeat the above two steps with the remaining integer part of the answer, until it is 0(zero):
  8 / 16 => 0.5
  0.5 * 16 => 8

This gives the hexadecimal number 86h.

---

To make it tougher; 51966 in hex is:
  51966 / 16 => 3247.875
  0.875 * 16 => 14 => E (hexadecimal representation of 14, remember?, put this farthest to the right)

  3247 / 16 => 202.9375
  0.9375 * 16 => 15 => F

  202 / 16 => 12.625
  0.625 * 16 => 10 => A

  12 / 16 => 0.75
  0.75 * 16 => 12 => C

That makes C A F E, CAFEh, which is a nice place to go when the coffe provided at work tastes too bad. Lots of nice other "things" there too, if you know what I mean!? >;->

And, BlackDeath...; could you please stop using this strange english syntax? I'm "0" as cool as "U" so I can "0" understand what "U" "R" trying "2" say... ;|

/// John

Author

Commented:
Hello John! Thanks.Now everything is clear. Finally understood how to convert one to another by hand. Once again thanks, and take care ;)

Regards,
Viktor Ivanov
sure, john - no problem.

it's just a bad habit from former times.
i'll try and have an eye on it.
but don't be angry when one or the other howler slips in, ok?

regards,

Black Death.


Commented:
No problem!
I'm not that stingy. Just thinking about all those with problems reading the marvelous english language. They're supposed to benefit from this too, right?

/// John
right you are
bye,
Black Death.
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