One 、 One dimensional array

  1. One dimensional array creation

int main() {
    
	int arr[8];// An array type   Array name [ Element number ];
	char ch[3];

	return 0;
}

   notes ： The number of elements must be a constant expression , Form like arr[n] The array of is created only in C99 Only supported under syntax , Some compilers can compile such code , But not recommended .

  2. One dimensional array initialization

int main() {
    
	int arr1[3] = {
     1, 2, 3 };// Fully initialized 
	int arr2[3] = {
     1, 2 };// Incomplete initialization 

	/*  The following two lines of code are equivalent  int arr3[3] = { 1, 2, 3 }; int arr3[] = { 1, 2, 3 }; */

	return 0;
}

   Pay attention to distinguish the following codes ：

int main() {
    
	char ch1[5] = {
     'b', 'i', 't' };
	char ch2[] = {
     'b', 'i', 't' };

	char ch3[5] = "bit";// b i t \0 0
	char ch4[] = "bit";// b i t \0

	return 0;
}

   because \0 It's the end sign , and ch2 did not \0, So it will continue to print , Until I find \0 until .

  3. One dimensional array memory storage

int main() {
    

	int arr[5];
	char ch[5];
	int i = 0;
	for (i = 0; i < 5; i++) {
    
		printf("arr[%d] = %p ", i, &arr[i]);//%p -  Print in address format  -  Hexadecimal printing 
		printf("ch[%d] = %p\n", i, &ch[i]);
	}

	return 0;
}

   As can be seen from the figure above , Every arr The size difference between the addresses of elements 4 Bytes , Every ch The size difference between the addresses of elements 1 Bytes . And one int The size of the type is just 4 byte , One char The size of the type is just 1 byte . therefore One dimensional arrays are stored continuously in memory , also As the address grows , The address changes from low to high .
   notes ： The address of the array name is the address of the first element of the array .

Two 、 Two dimensional array

  1. The creation of two-dimensional array

int main() {
    
	// establish 
	// An array type   Array name [ Number of line elements ][ Number of column elements ];
	int arr[3][4];
	char ch[3][4];

	return 0;
}

  2. 2D array initialization

int main() {
    
	// initialization  -  Create and assign values at the same time 
	int arr1[3][4] = {
     1,2,3,4,5,6,7,8,9,10,11,12 };
	int arr2[3][4] = {
     1,2,3,4,5,6,7 };// Incomplete initialization  -  Back up 0
	int arr3[3][4] = {
     {
    1, 2}, {
    3, 4}, {
    5, 6} };
	int arr4[][4] = {
     {
    1, 2}, {
    3, 4}, {
    5, 6} };// Lines can be omitted , But the column cannot be omitted 

	return 0;
}

   notes ： For code Readability , It is recommended to use one for each line {} Cover up , It can be understood that a two-dimensional array is understood as a one-dimensional array with several groups of one-dimensional arrays .

  3. Memory storage of two-dimensional array

int main() {
    
	int arr[3][4] = {
     {
    1,2},{
    3,4},{
    5,6} };
	int i = 0;
	int j = 0;
	for (i = 0; i < 3; i++) {
    
		for (j = 0; j < 4; j++) {
    
			printf("arr[%d][%d] = %p\n", i, j, &arr[i][j]);
		}
	}

	return 0;
}

   As can be seen from the figure above , Every arr The size difference between the addresses of elements is still 4 Bytes , The last element of the first line and the first element of the second line The size difference between them is also 4. therefore Two dimensional arrays are also stored continuously in memory , It's also As the address grows , The address changes from low to high .