Array of C language

Catalog

One dimensional array creation and initialization

The way one-dimensional arrays are created

Initialization of an array

The use of one-dimensional arrays

One dimensional array storage in memory

The creation and initialization of two-dimensional array

The creation of two-dimensional array

  initialization —— Assign value to it while creating

The use of two-dimensional arrays

Storage of two-dimensional array in array

Arrays as function arguments

character string

One dimensional array creation and initialization

Array ： A collection of elements of the same type

The way one-dimensional arrays are created

// Array initialization instance 
	int arr1[3];
	char arr2[8];
	double arr3[20];

Be careful ： Array creation ,[] You have to give a constant in the , You can't use variables

Initialization of an array

The initialization of an array refers to , While creating the array, give some reasonable initial values to the contents of the array （ initialization ）

	// Fully initialized 
	int arr1[10] = {1,2,3,4,5,6,7,8,9,10};
	// Incomplete initialization （ The array length is 10, after 5 A complement 0）
	int arr2[10] = { 1,2,3,4,5 };
	// Determine the initialization of the array length according to the initialization content 
	int arr3[] = {1,2,3,4,5,6};// The array length is 6
	// The first way to write a character array 
	char ch1[5] = "bit";// Incomplete initialization , Later use '\0' Add 
	char ch2[] = "bit";// The array length is 3
	// The second way to write a character array 
	char ch3[] = { 'b','i','t' };// altogether 3 Elements 
	char ch4[6] = { 'b','i','t' };// altogether 6 Elements , For the other '\0'

The use of one-dimensional arrays

[]： Subscript reference operator , Access elements in an array by subscript , Array index from 0 Start

#include <stdio.h>
int main() {
	int arr1[10] = { 0 };
	arr1[4] = 5;// Will array the 5 The number is changed to 5
	int sz = sizeof(arr1) / sizeof(arr1[0]);
	// Traversal array 
	int i = 0;
	for (i = 0; i < sz; i++) {
		printf("%d\n", arr1[i]);
	}
	return 1;
}

One dimensional array storage in memory

• Each element of a one-dimensional array is stored continuously in memory
• As the array subscript grows , The address changes from low to high
• The array name is the address of the first element

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The creation and initialization of two-dimensional array

The creation of two-dimensional array

  initialization —— Assign value to it while creating

	// Fully initialized 
	int arr1[3][4] = {1,2,3,4,5,6,7,8,9,10,11,12};
	// Incomplete initialization —— Back up 0
	int arr2[3][4] = {1,2,3,4,5,6,7};
	// The second method 
	int arr3[3][4] = { {1,2},{3,4},{4,5} };// Not completely initialized here , The last two columns are supplemented 0
	// The second method is to determine the number of rows according to the following elements , But there are several elements in a line that cannot be omitted 
	int arr3[][4] = { {1,2},{3,4},{4,5} };

The use of two-dimensional arrays

The operation of two-dimensional array is also through subscript [][]

#include <stdio.h>
int main() {
	// Traversing a two-dimensional array 
	int arr1[][4] = { {1,2},{3,4},{4,5} };
	int i = 0;
	int j = 0;
	for (i = 0; i < 3; i++) {
		for (j = 0; j < 4; j++) {
			printf("%d ", arr1[i][j]);
		}
		printf("\n");
	}
	return 1;
}

Storage of two-dimensional array in array

• Two dimensional arrays are also stored continuously in memory （ A row is internally continuous , Line breaks are also continuous ）
• A two-dimensional array stored in memory is a very long one-dimensional array

#include <stdio.h>
int main() {
	// Traversing a two-dimensional array 
	int arr1[][4] = { {1,2},{3,4},{4,5} };
	int i = 0;
	int* p = &arr1[0][0];
	for (i = 0; i < 12; i++) {
		printf("%d ", *p);
		p++;
	}
	return 1;
}

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Arrays as function arguments

When an array passes parameters, it passes the address of the first element of the array

The array name is the address of the first element of the array, but it has 2 Exceptions

• sizeof( Array name ）—— The array name indicates that the size of the entire array is calculated, and the unit is bytes
• & Array name —— The array name represents the entire array , It takes out the address of the entire array

In addition, all array names are the addresses of the first elements of the array  

#include <stdio.h>
int main() {
	int arr[10] = { 0 };
	printf("%p\n", arr);
	printf("%p\n", arr+1);// Bad 4
	printf("%p\n", &arr);
	printf("%p\n", &arr+1);// Bad 40
	return 1;
}

#include <stdio.h>
void main() {
	int a[] = { 1,2,3,4 };
	printf("%d\n", sizeof(a));//16—— The size of the entire array 
	printf("%d\n", sizeof(a+0));//4—— The address of the first element 
	printf("%d\n", sizeof(*a));//4—— The first element of the array 
	printf("%d\n", sizeof(a+1));//4—— The address of the second element 
	printf("%d\n", sizeof(a[1]));//4—— The second element of the array 
	//&a
	printf("%d\n", sizeof(&a));//4—— Address of array , The address is generally 4（32 position ）
	printf("%d\n", sizeof(*&a));//16—— The size of the entire array 
	printf("%d\n", sizeof(&a+1));//4—— It's an address （ The address of the space behind the array ）, The address is generally 4（32 position ）
	printf("%d\n", sizeof(&a[0]));//4—— The address of the first element of the array 
	printf("%d\n", sizeof(&a[0]+1));//4—— The address of the second element of the array 
}

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character string

Definition ： A string of characters enclosed by double quotation marks is called the literal value of the string , Or string , It's an array

Be careful ： The end of a string is a \0 The escape character of , When calculating the length of a string \0 It's the end sign , Does not count as the contents of the string .

What is wrapped in single quotation marks is a character constant , What is wrapped in double quotation marks is a string, which can wrap multiple characters ;

int main() {
	char a[] = "abc";
	char b[] = { 'a','b','c' };
	printf("%s\n", a);
	printf("%s", b);
}

Print the results ：

  reason ： The end flag of the string is \0,b No, I didn 't \0 Will continue to print backwards until you find \0