A variable name can only begin with an alphabet and an underscore. It cannot start with numbers. These variables are declared with the registry keyword. Note that it is common among Stata users to use all lowercase letters for variable names, although this is not a requirement, whereas in SPSS variable names are not case-sensitive. After you declare variables, you can assign a value to a variable later by using a statement similar to the following: As the last example shows, some words are reserved as keywords in the language and cannot be used as variable names. Depending on the scope, C variables can be divided into two types: Although the idea of a variable that never changes doesn`t make sense, there are good reasons to use const. For one, many compilers can make a few small adjustments to the data if they know the data will never change. For example, if you need the value of π in your calculations, you can declare a variable const of pi so that a program or other function written by someone else cannot change the value of pi. Variable names in C consist of letters (case sensitive) and numbers. The underscore (“_”) is also allowed. Names cannot begin with a number.
Unlike some languages (such as Perl and some BASIC dialects), C does not use special prefix characters for variable names. All local variables are automatic variables by default. They are also known as autovariates. Variable initialization is the process by which the user assigns a meaningful value to the variable. When you run the above program, the following output is generated: So far, we have only seen variables whose values can be changed as often as desired. But C also offers us a way to make the value of a variable immutable. We can do this by setting the variable as a constant. To use a variable in C, it must first be defined to inform the compiler of its existence so that the compiler can allocate the necessary memory. Because C is a relatively weak programming language, before a C program can use memory to store a variable, it must consume the memory needed to store the values of a variable. This is done by declaring variables. Variable declaration is how a C program displays the number of variables needed, their names, and the amount of memory they need. 1.
A variable name can consist of letters, numbers, and underscores ( _ ). It is not acceptable to use the same name for multiple variables in the same range. Therefore, when collaborating with other developers, you should take steps to avoid using the same name for global variables or function names. Some large projects follow naming guidelines to avoid duplicate names and ensure consistency. You can also assign variables to the value of another variable, as follows: their scope is local and their lifetime is until the end of the block. If necessary, we can use the auto keyword to define the automatic variables. In addition, all variable names in the str#### pattern (“str” followed by a number) are also invalid (reserved in stata). Long and short are modifiers that allow a data type to use more or less memory. The int keyword does not need to track short and long keywords. This is most often the case. A short can be used when the values are in a smaller range than an int, usually -32768 to 32767. A long can be used to hold a wide range of values.
It is not guaranteed that a short consumes less memory than an int, nor that a long one consumes more memory than an int. It is only guaranteed that sizeof(short) <= sizeof(int) <= sizeof(long). Typically, a short one is 2 bytes, an int is 4 bytes, and a long one is 4 or 8 bytes. Modern C compilers also offer long long, which is usually an 8-byte integer. Like most programming languages, C uses and processes variables. In C, variables are human-readable names for computer memory addresses used by a running program. Variables make it easier to store, read, and modify data in your computer`s memory by allowing you to assign easy-to-remember labels to memory addresses where your program`s data is stored. The memory addresses associated with the variables are not determined until the program is compiled and run on the computer. In the example above, we can see that the local variable always generates the same value when the function is called, while the static variable generates the incremental value in each function call.
If you declare a function or global variable as static, you cannot access the function or variable from other files in your project using the external keyword (see below). This is called a static link. Local variables in C are variables declared in a function or code block.