Connect and share knowledge within a single location that is structured and easy to search. Why are hexadecimal numbers prefixed as 0x? I understand the usage of the prefix but I don't understand the significance of why 0x was chosen. Something is still needed to specify the number base: the x is an arbitrary choice. The BCPL language used the syntax 8 for octal numbers. This is great because. When C was created from B, the need for hexadecimal numbers arose the PDP had bit words and all of the points above were still valid.
Since octals were still needed for other machines, 0x was arbitrarily chosen 00 was probably ruled out as awkward. Imagine needing to come up with a system to denote hexadecimal numbers, and note we're working in a C style environment. How about ending with h like assembly?
Unfortunately you can't - it would allow you to make tokens which are valid identifiers eg. In the end, for whatever reason, they decided to put an x after a leading 0 to denote hexadecimal.
It is unambiguous since it still starts with a number character so can't be a valid identifier, and is probably based off the octal convention of a leading 0.
It's a prefix to indicate the number is in hexadecimal rather than in some other base. The C programming language uses it to tell compiler. When compiler reads 0x , It understands the number is hexadecimal with the help of 0x term. Usually we can understand by 16 or 8 or whatever.. I don't know the historical reasons behind 0x as a prefix to denote hexadecimal numbers - as it certainly could have taken many forms.
This particular prefix style is from the early days of computer science. However, for programming purposes we often need to distinguish the bases from binary base-2 , octal base-8 , decimal base and hexadecimal base - as the most commonly used number bases. At this point in time it is a convention used to denote the base of a number. I've written the number 29 in all of the above bases with their prefixes:.
Basically, an alphabet we most commonly associate with a base e. This is especially helpful because smaller numbers can confusingly appear the same in all the bases: 0b1, 0o1, 0d1, 0x1. If you were using a rich text editor though, you could alternatively use subscript to denote bases: 1 2 , 1 8 , 1 10 , 1 How are we doing?
Please help us improve Stack Overflow. It has already been answered by Lucas that "0x prefix identifies the number that follows as a hexadecimal constant", but I want to complement the answer with some relevant details:. P: To use a prefix? A: To differentiate from a decimal, since hexa is perfectly normal with no letter at all.
A single hexadecimal digit can represent four binary digits! So how do we convert between number systems? First consider how we determine the value of a decimal number. The base of a decimal number is Each digit has to be scaled according to its place within the number. The scale of the digit is the base of the number system raised to the power of the digit's location in the number. So each number is scaled, and then all of the scaled digits are added to find the total value of the number.
The same method can be used to find the value of a binary number. The base of the binary system is 2 the prefix 0b is often used in code to indicate that the number is in the binary format. What a completely inefficient way of typing a number! But we can represent the same binary number using only 2 hexadecimal digits.
First though, we'll start by converting a hexadecimal hex number to decimal like we did for a binary number. How about 0xB5? BCPL evolved over quite short time. While from start on was used to mark an octal number, it got soon supplemented by b for binary x for hexadecimal and even o for octal. These additions were time and implementation specific, but at least x became quick a standard. C in turn was developed for the PDP, for which, as 16 bit machine, many machine dependent constants come naturally in hex - not to mention the 8 bit byte and ASCII's segmentation in groups of Now reintroducing a hex notation was considered useful - just this time staying with the idea of a preceding zero.
While it already has many of the basics of C, like pointers to words as basic element,it also contains several features that seem quite unconventional from today. Multi-character identifiers had to start with capital letters. This might as well be the origin of the much liked camel case. So while I know of no direct relation, it's quite interesting that they came up with the same solution at the same time as Thompson did.
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