I have found out that 015 is an octal code. Then what is the term for "\r"? What kind of system is that? And why isn't there a system where I just enter the decimal value of the ASCII table, like e.g. "\13" for a carriage return?
why isn't there a system where I just enter the decimal value of the ASCII table, like e.g. "\13" for a carriage return?
For historical reasons, most systems allow direct representation of characters in hexadecimal and/or octal
This is because although humans used to base 10 find decimal easier, octal and hexadecimal are easier to understand at the bit level
Each octal digit is exactly 3 bits and each hexadecimal digit is 4 bits, whereas base 10 digits do not not exactly fit a fixed number of bits
If you wish to make arbitary characters based on decimal codes, there is usually function for this. For example in python
python -c 'print chr(13)'
This will output the carriage return character you are interested in
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I want to know how many characters or numbers can I store in 1 bit only. It will be more helpful if you tell it in octal, hexadecimal.
I want to know how many characters or numbers can I store in 1 bit only.
It is not practical to use a single bit to store numbers or characters. However, you could say:
One integer provided that the integer is in the range 0 to 1.
One ASCII character provided that the character is either NUL (0x00) or SOH (0x01).
The bottom line is that a single bit has two states: 0 and 1. Any value domain with more that two values in the domain cannot be represented using a single bit.
It will be more helpful if you tell it in octal, hexadecimal.
That is not relevant to the problem. Octal and hexadecimal are different textual representations for numeric data. They make no difference to the meaning of the numbers, or (in most cases1) the way that you represent the numbers in a computer.
1 - The exception is when you are representing numbers as text; e.g. when you represent the number 42 in a text document as the character '4' followed by the character '2'.
A bit is a "binary digit", or a value from a set of size two. If you have one or more bits, you raise 2 to the power of the number of bits. So, 2¹ gives 2. The field in Mathematics is called combinatorics.
Is there a way to compress/encode string to specified length(8/10 character).
I have a combination of secret key and a numeric value of 16 digit, and I want to create a unique id with combination of these both. which length should be between 8-12, and it should not change if combination is same.
Please suggest a way.
If it's 16 decimal digits and your string can contain any characters, then sure. If you want ten characters out, then you'd need 40 different characters. 4010 > 1016. Or for nine characters out, you need 60 different characters. 609 > 1016. E.g. some subset of the upper case letters, lower case letters, and digits (62 to choose 40 or 60 from). Then it is simply a matter of base conversion either way. Convert from base 10 to base 40 or 60, and then back.
Many languages already have Base-64 coding routines, which will get you to nine characters.
Eight is a problem, since you would need 100 characters (1008 == 1016), and there are only 95 printable ASCII characters.
You could use a secure hash function, like sha512, and truncate the resulting hex string to the desired length.
If you want slightly more entropy, you can base64 encode it before truncating.
I just have a question to make sure I get something well.
If I used my computer to sum 10+11 which is 21, it will store 21 in usually a byte such that 0001 0101, however, when it prints it on the screen, it will actually represent it as two digits 2 (0110010) and 1 (0110001) appended to each other to form 21) using ASCII.
Is that right?
Thank you!
That is correct.
The representation of characters in a simple terminal is ASCII, where each character is represented by a (technically 7-bit) code.
Some terminals support more complex encodings like UTF8, but since UTF8 is backwards compatible with ASCII you need not worry about it.
I want to print the value '½' in a file. I searched for the ascii value of this as Alt+(ascii Value) will give you the same. To my surprise I found 2 ascii values for this symbol in various sites. One is 171 and the other is 189.
I tried to write this symbol by using 171 and 189. Again to my surprise, if I am writing in Windows, 171 will give me this symbol. But if I am writing in UNIX, 189 will give me this symbol.
I was aware that there cant be 2 ASCII Values for a same symbol. But I got 2 valid codes for the same symbol in different OS. So can anyone tell what is the real ASCII Code for the symbol ½ ??
½ is not a character in the ASCII character set.
The values you're finding online probably differ because they're using different character sets. For example, before Unicode was invented, localized versions of Windows all used different code pages, in which the basic ASCII set was extended with some additional characters.
Now, of course, everything is (or should be) fully Unicode. Detailed Unicode information for that character (vulgar fraction one half) can be found here. Note that there are also multiple representations for the same numerical value (e.g., base 10, hex, binary, etc.).
In Windows if you use the ALT codes,
3 digits will insert the equivalent "Code page 850" character
so ALT + 171 will insert the ½ symbol
189 is the ANSI/UTF-8/WIN-1252/ISO8859-1 value for the ½ symbol.
To use ALT codes for ANSI you MUST press 0 first,
so ALT + 0189 inserts the ½ symbol
Please read the ASCII wikipedia page. You'll learn that ASCII has no "one half" character.
These days, most systems can be configured to use UTF-8 encoding (which is the "default" or at least the most commonly used encoding on the Web and on Unix systems).
UTF-8 is a variable length encoding for Unicode. So many characters or glyphs are represented by several bytes. For the ½ (officially the vulgar fraction one half unicode character) its UTF8 encoding is the two hex bytes 0Xc2 0xBD so in C notation \302\275
I am using the Linux Gnome Character Map utility gucharmap to find all that.
You might be interested in UTF-32 (a fixed length encoding using 32 bits characters, in which ½ is represented by 0x000000BD), or even UTF-16 in which many characters are 16 bits (in particular ½ is 0x00BD e.g. one 16 bit character in UTF-16), but not all. You may also be interested in wide characters i.e. the wchar_t of recent C or C++ standards (which is UTF-16 on Windows and UTF-32 on many Unix).
FWIW, Qt is using QChar as UTF-16 (Java also has UTF-16 char ...), but Gtk use UTF-8 i.e. variable length characters.
Notice that with variable length character encodings like UTF-8 getting the N-th character (which is not the N-th byte!) in a string requires to scan the string. Also, some byte combinations are not valid UTF-8.
As others have pointed out: it's not in the ASCII table (values 0..127).
But it has a Unicode code of:
½ U+00BD Vulgar Fraction One Half
It can also be put into text using the unicode U+2044 Fraction Slash:
where your text contains the three code points: 1⁄2
but it gets rendered as 1⁄2
This has the virtue of working for any fractions:
1⁄2
3⁄5
22⁄7
355⁄113
355⁄113 - 1⁄3748629
I am quite sure that it is indeed part of the ASCII Table:
In Windows, ensure 'NumLock' is on then try [ALT + (NumPAD)171] = ½.
For ¼ use [ALT + 172]
I need to enter a string and to show that string like array of ASCII codes.
How can i implement it in assembly language.
In assembly language, characters are already encoded in ASCII (or unicode or whatever). You work with characters as numbers.
What you need to be able to is to format numbers in their denary representation, for output. This is not specific to character codes.
There will almost certainly be library routines to do this, but it's not hard to do yourself. Basically, you write a loop which repeatedly extracts the lowest digit from the number (by taking the residue of the number modulo 10 - look for a MOD instruction), converts that into the character code for a digit (by adding 48) and adds it to a buffer, then divides the number by 10 to move on to the next digit. You repeat that until the number is zero.