C Tutorials
| Variable |
A variable is named location in memory. Each variable in C has a specific type, which determines the size and layout of the variable's memory; the range of values that can be stored within that memory; and the set of operations that can be applied to the variable.
The name of a variable can be composed of letters, digits, and the underscore character. It must begin with either a letter or an underscore. Upper and lowercase letters are distinct because C is case-sensitive. Based on the basic types explained in previous chapter, there will be following basic variable types:
| Type | Description |
| char | Integer type, Single byte of storage |
| int | Natural size of the integer for the machine usually 2 bytes |
| float | A single-precision floating point value. |
| double | A double-precision floating point value. |
| void | Represents the absence of type. |
| Variable Declaration |
All variables must be declared before we use them in C program, although certain declarations can be made implicitly by content. A declaration specifies a type, and contains a list of one or more variables of that type as follows:
type var_list;
Here, type must be a valid C data type including char, int, float, double, or any user defined data type etc., and var_list may consist of one or more identifier names separated by commas. Some valid variable declarations along with their definition are shown here:
int a,b,c;
char ch;
float f;
double d;
We can initialize a variable at the time of declaration as follows:
int a=10;
An extern declaration is not a definition and does not allocate storage. In effect, it claims that a definition of the variable exists some where else in the program. A variable can be declared multiple times in a program, but it must be defined only once. Following is the declaration of a variable with extern keyword:
extern int a;
| Variable Initialization |
var_name=value;
Variables can be initialized (assigned an initial value) in their declaration. The initializer consists of an equal sign followed by a constant expression as follows:
type var_name=value;
#include<stdio.h>
void main()
{
int a,b,c;
a=10;
b=5;
c=a+b;
printf("\nSum of a and b is:%d",c);
}
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