[C language] analysis of variable essence

Catalog

1、 Variable concept

2、 The nature of variables

3、 Experimental verification

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1、 Variable concept

Objects that can read and write memory variables are called variables ;

Objects that cannot be modified once initialized are called constants ;

Definition of variables

Type the name   identifier 、 identifier ;

for example ：

int i,j,m,n;
char num;
double k;
float fan;

2、 The nature of variables

（1） The program uses variables to apply for and name memory space int a = 0

（2） Access memory space by variable name

（3） There are ways to modify variables ？？？

• direct , Change the value of the variable ;
• indirect , Get the address number of the variable , You can modify variables ;

Define variables by data types ;

3、 Experimental verification

• Read and write variables ;
• Read and write data to memory through variables ;
• Not reading and writing data to variables , Instead, write data to the memory space represented by the variable ;

Three elements of variable ( name 、 size 、 Scope ).

#include <stdio.h>

int main(){
    // Operating memory through variables 
    int n = 10;
    printf("&n:%d\n",&n);

    // Modify variables by memory address , among &n = 6356508
    *((int*)(6356508)) = 20;
    printf("n = %d\n",n);

    return 0;
}

Result display ：