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For example, \11 is an octal escape sequence denoting a byte with decimal value 9 (11 in octal). However, \1111 is the octal escape sequence \111 followed by the digit 1 . In order to denote the byte with numerical value 1, followed by the digit 1 , one could use "\1""1" , since C concatenates adjacent string literals.
In C and many derivative programming languages, a string escape sequence is a series of two or more characters, starting with a backslash \. [3]Note that in C a backslash immediately followed by a newline does not constitute an escape sequence, but splices physical source lines into logical ones in the second translation phase, whereas string escape sequences are converted in the fifth ...
Each of these number systems is a positional system, but while decimal weights are powers of 10, the octal weights are powers of 8 and the hexadecimal weights are powers of 16. To convert from hexadecimal or octal to decimal, for each digit one multiplies the value of the digit by the value of its position and then adds the results. For example:
Octal Description # ASCII Punctuation & Symbols: U+0020 32 040 Space: 0001 U+0021 ! 33 041 Exclamation mark: 0002 U+0022 " 34 042 Quotation mark: 0003 U+0023 # 35 043 Number sign, Hash, Octothorpe, Sharp: 0004 U+0024 $ 36 044 Dollar sign: 0005 U+0025 % 37 045 Percent sign: 0006 U+0026 & 38 046 Ampersand: 0007 U+0027 ' 39 047 Apostrophe: 0008 U+ ...
To convert integer decimals to octal, divide the original number by the largest possible power of 8 and divide the remainders by successively smaller powers of 8 until the power is 1. The octal representation is formed by the quotients, written in the order generated by the algorithm. For example, to convert 125 10 to octal: 125 = 8 2 × 1 + 61
The formatting placeholders in scanf are more or less the same as that in printf, its reverse function.As in printf, the POSIX extension n$ is defined. [2]There are rarely constants (i.e., characters that are not formatting placeholders) in a format string, mainly because a program is usually not designed to read known data, although scanf does accept these if explicitly specified.
In C and C++, a leading zero indicates an octal value, e.g. 0755. This was primarily intended to be used with Unix modes; however, it has been criticized because normal integers may also lead with zero. [19] As such, Python, Ruby, Haskell, and OCaml prefix octal values with 0O or 0o, following the layout used by hexadecimal values.
Or if the backslash is followed by 1-3 octal digits, then this sequence is interpreted as representing the arbitrary code unit with the specified value in the literal's encoding (for example, the corresponding ASCII code for an ASCII literal). This was later extended to allow more modern hexadecimal character code notation: