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In contrast to literals, variables or constants are symbols that can take on one of a class of fixed values, the constant being constrained not to change. Literals are often used to initialize variables; for example, in the following, 1 is an integer literal and the three letter string in "cat" is a string literal:
The length of a string can also be stored explicitly, for example by prefixing the string with the length as a byte value. This convention is used in many Pascal dialects; as a consequence, some people call such a string a Pascal string or P-string. Storing the string length as byte limits the maximum string length to 255.
A string literal or anonymous string is a literal for a string value in the source code of a computer program. Modern programming languages commonly use a quoted sequence of characters, formally "bracketed delimiters", as in x = "foo", where , "foo" is a string literal with value foo. Methods such as escape sequences can be used to avoid the ...
For example, the constant 3HABC specified a three-character string "ABC", identified by the initial integer representing the string length 3 and the specified Hollerith character H, followed by the string data ABC. These constants were typeless, so that there were no type conversion issues. If the constant specified fewer characters than was ...
The most significant are: compile-time (statically valued) constants, run-time (dynamically valued) constants, immutable objects, and constant types . Typical examples of compile-time constants include mathematical constants, values from standards (here maximum transmission unit), or internal configuration values (here characters per line ...
Constants may optionally be prefixed with a lowercase letter "k" like kCFBooleanTrue. Instance variables of an object use lowerCamelCase prefixed with an underscore, like _delegate and _tableView . Method names use multiple lowerCamelCase parts separated by colons that delimit arguments, like: application:didFinishLaunchingWithOptions ...
because the argument to f must be a variable integer, but i is a constant integer. This matching is a form of program correctness, and is known as const-correctness.This allows a form of programming by contract, where functions specify as part of their type signature whether they modify their arguments or not, and whether their return value is modifiable or not.
A string is defined as a contiguous sequence of code units terminated by the first zero code unit (often called the NUL code unit). [1] This means a string cannot contain the zero code unit, as the first one seen marks the end of the string. The length of a string is the number of code units before the zero code unit. [1]