不变
顾名思义,C 编程语言中的变量或值被赋予名称常量,一旦定义就不能修改。它们是程序中的固定值。可以有任何类型的常量,如整数、浮点数、八进制、十六进制、字符常量等。每个常量都有一定的范围。太大而无法放入 int 的整数将被视为 long。现在有各种不同的范围,从无符号位到有符号位。在有符号位下,int 的范围从 -128 到 +127,在无符号位下,int 的范围从 0 到 255。
例子:
#include
// Constants
#define val 10
#define floatVal 4.5
#define charVal 'G'
// Driver code
int main()
{
printf("Integer Constant: %d\n", val);
printf("Floating point Constant: %f\n", floatVal);
printf("Character Constant: %c\n", charVal);
return 0;
}
输出:
Integer Constant: 10
Floating point Constant: 4.500000
Character Constant: G
多变的
简单来说,变量就是分配了一些内存的存储位置。基本上,用于存储某种形式的数据的变量。不同类型的变量需要不同的内存量,并且有一些可以应用于它们的特定操作集。
变量声明:
典型的变量声明格式如下:
type variable_name;
or for multiple variables:
type variable1_name, variable2_name, variable3_name;
变量名可以由字母(大写和小写)、数字和下划线“_”字符。但是,名称不得以数字开头。
例子:
#include
int main()
{
// declaration and definition of variable 'a123'
char a123 = 'a';
// This is also both declaration
// and definition as 'b' is allocated
// memory and assigned some garbage value.
float b;
// multiple declarations and definitions
int _c, _d45, e;
// Let us print a variable
printf("%c \n", a123);
return 0;
}
输出:
a
变量和常量的区别
Constants | Variable |
---|---|
A value that can not be altered throughout the program | A storage location paired with an associated symbolic name which has a value |
It is similar to a variable but it cannot be modified by the program once defined | A storage area holds data |
Can not be changed | Can be changed according to the need of the programmer |
Value is fixed | Value is varying |
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