当前课程知识点：C Programming > Chapter 8 Pointer > 8.3 Pointer of array element, operation of pointer and reference of array element by pointer > 8.3 Pointer of array element, operation of pointer and reference of array element by pointer.mp4
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欢迎走进C语言程序设计课堂
今天我们讲解数组元素的指针
指针的运算以及通过指针引用数组元素
指针变量既然可以指向变量
当然也可以指向数组元素
把某一元素的地址放到一个指针变量中
下面介绍数组元素的指针，即数组元素的地址
一个变量有地址，一个数组包含若干元素
每个数组元素都有相应的地址
指针变量可以指向数组元素
所谓数组元素的指针就是数组元素的地址
可以用一个指针变量指向一个数组元素，例如
int a[10]并进行初始化
int *p; p=&a[0]; 这两个语句
等价于int *p=a; 或int *p=&a[0];的地址
以上是使指针变量p指向a数组的第0号元素，如图所示
注意：
“p=a;”的作用是“把a数组的首元素的地址
赋给指针变量p”，而不是“把数组a各元素的值赋给p”
引用数组元素可以用下标法（如a[3]）
也可以用指针法，即通过指向数组元素的指针
找到所需的元素，使用指针法能使目标程序质量高
占内存少，运行速度快
在C语言中，数组名
不包括形参数组名，形参数组名并不占据实际的内存单元
不代表整个数组，只代表数组首元素
（即序号为0的元素）的地址
因此，下面两个语句等价：
p=&a[0]; 地址
p=a;
在引用数组元素时常常会遇到指针的算术运算
那么在什么情况下需要用到对指针型数据的算术运算呢？
显然对地址进行乘和除的运算是没有意义的
实际上也无此必要，那么能否进行加和减的运算？
答案是：在一定条件下允许对指针进行加和减的运算
在指针指向数组元素时，允许以下运算：
加一个整数(用+或+=)，如p+1
减一个整数(用-或-=)，如p-1
自加运算，如p++，++p
自减运算，如p--，--p
两个指针相减，如p1-p2
只有p1和p2都指向同一数组中的元素时才有意义
(1) 如果指针变量p已指向数组中的一个元素
则p+1指向同一数组中的下一个元素
p-1指向同一数组中的上一个元素
float a[10],*p=a;
假设a[0]的地址为2000，则
p的值为2000
p+1的值为2004
P-1的值为1996
(2) 如果ｐ的初值为&a[0]
则p+i和a+i就是数组元素a[i]的地址
或者说，它们指向a数组序号为i的元素，如图所示
(3) *(p+i)或*(a+i)是p+i或a+i所指向的数组元素
即a[i]。
如图所示
(4) 如果指针p1和p2都指向同一数组
p2-p1的值是4
不能p1+p2运算
下面介绍通过指针引用数组元素
下面来看例8.6 有一个整型数组a
有10个元素，要求输出数组中的全部元素。
解题思路：引用数组中各元素的值有3种方法
(1)下标法
(2)通过数组名计算数组元素地址，找出元素的值
(3) 用指针变量指向数组元素
分别写出程序，以资比较分析。
(1) 下标法
{ int a[10]; int i;
循环10次，输出a[i]的值
程序运行结果如图所示
输入10个数，0到9
输出10个数，0到9
(2) 通过数组名计算数组元素地址，找出元素的值
{ int a[10]; int i;
for(i=0;i<10;i++) scanf("%d",&a[i]); 等价于scanf("%d",a+i);
for(i=0;i<10;i++)
printf(“%d ”,*(a+i));
(3) 用指针变量指向数组元素
{ int a[10]; int *p,i;
循环10次，输入a[i]的值
for(p=a;p<(a+10);p++)
printf(“%d ”,*p);
程序中
for(i=0;i<10;i++) scanf("%d",&a[i]); 可以写为
for(p=a;p<(a+10);p++)
scanf("%d",p);
但如果将
printf(“%d ”,*p);
写成printf(“%d ”,*a); 则是错误的
3种方法的比较：
① 第(1)和第(2)种方法执行效率相同
Ｃ编译系统是将a[i]转换为*(a+i)处理的
即先计算元素地址
因此用第(1)和第(2)种方法找数组元素费时较多
② 第(3)种方法比第(1)、第(2)种方法快
用指针变量直接指向元素，不必每次都重新计算地址
像p++这样的自加操作比较快
这种有规律地改变地址值(p++)能大大提高执行效率
③ 用下标法比较直观，能直接知道是第几个元素。
用地址法或指针变量的方法不直观
难以很快地判断出当前处理的是哪一个元素
下面来看例8.7 通过指针变量输出整型数组a的10个元素
解题思路：
用指针变量p指向数组元素
通过改变指针变量的值，使p先后指向a[0]到a[9]各元素
程序如下所示
{ int *p,i,a[10];
p=a;
for(i=0;i<10;i++) scanf(“%d”,p++);
退出循环时p指向a[9]后面的存储单元
for(i=0;i<10;i++,p++)
printf(“%d ”,*p);
因此执行此循环出问题
要改正则应当在输出语句前，须重新执行p=a; 即
p=a;
for(i=0;i<10;i++,p++)
printf(“%d ”,*p);
好了，同学们，数组元素的指针
指针的运算以及通过指针引用数组元素我们就学习到这儿
下节课再见！
-1.1 The development and characteristics of C language
--1.The development and characteristics of C language .mp4
--1.1 Self test questions
-1.2 A simple C Language program
--1.2 A simple C Language program.mp4
--【Source program】 Example 1.1 output a line of text Hello, world! "
--【Source program】 Example 1.2 program composed of multiple functions, find the larger of two integers
--1.2 Self test questions
-1.3 Program, Programming Language and C Program Running Steps
--1.3 Program, Programming Language and C Program Running Steps.mp4
--Running steps of C source program in CodeBlocks
--1.3 Self test questions
-chapter 1 Self-Test
-2.1 The Concept and Description of Algorithms
--2.1 The Concept and Description of Algorithms.mp4
--2.1 Self test questions
-2.2 Examples of Simple Algorithms, Computational Thinking and Structured Programming
--2.2 Examples of Simple Algorithms, Computational Thinking and Structured Programming.mp4
--2.2 Self test questions
-Chapter 2 Self test questions
-3.1 Simple Structure and Identifier of C Language Program
--3.1 Simple Structure and Identifier of C Language Program.mp4
--【Source program】 Example 3.1 input two integers and output the sum of two numbers.
--【Source program】 Example 3.2 input two integers and output the average value.
--【Source program】 Example 3.3 output the value of the character variable.
--3.1 Self test questions
-3.2 Constants, Variables and Assignments
--3.2 Constants, Variables and Assignments.mp4
--3.2 Self test questions
-3.3 Arithmetic, assignment, increment and decrement operators
--3.3 Arithmetic, assignment, increment and decrement operators.mp4
--3.3 Self test questions
-3.4 Conditions, commas, addresses, byte operators, and mixed operations among various numerical data
--3.4 Conditions, commas, addresses, byte operators, and mixed operations among various numerical data
--【Source program】 example of sizeof
--3.4 Self test questions
-3.5 Input and Output Examples and Character Input and Output
--3.5 Input and Output Examples and Character Input and Output.mp4
--【Source program】 Example. Find the root of quadratic equation of one variable.
--【Source program】 Example 1. Successively output three characters of BOY.
--【Source program】Example 2. Input 3 characters of BOY from the keyboard and output them to the screen
--3.5 Self test questions
-3.6 Formatted output printf function
--3.6 Formatted output printf function.mp4
--【Source program】 Example 3.4 output of integer data.
--【Source program】 Example 3.5 real data output.
--【Source program】 Example 3.6 character data output.
--【Source program】 Example 3.7 uses %s to output a string.
--3.6 Self test questions
-3.7 Formatted input scanf function
--3.7 Formatted input scanf function.mp4
--【Source program】 Example 3.8 Input and output integer data
--【Source program】Example 3.9 Input and output single precision and double precision real data.
--【Source program】Example 3.10 input and output character data.
--【Source program】Example 3.11 input and output string.
--3.7 Self test questions
-3.8 Basic Data Types of C Language
--3.8 Basic Data Types of C Language.mp4
--3.8 Self test questions
-Chapter 3 Self test questions
-Operator and expression self test questions
-4.1 Relational operators, logical operators, and if statements
--4.1 Relational operators, logical operators, and if statements.mp4
--【source example】Example 4.1 Find the root of the quadratic equation of one variable.
--【Source program】Example 4.2 Input two real numbers and output them from small to large.
--4.1 Self test questions
-4.2 Switch Statement
--【Source program】Example 4.3 uses switch statement to implement simple menu program
--【Source program】Example 4.4 converts centesimal score into the corresponding grade system score.
--4.2 Self test questions
-4.3 Examples of Selection Structural Programs
--4.3 Examples of Selection Structural Programs.mp4
--【Source program】 Example 4.5 determines whether a year is a leap year.
--【Source program】 Example 4.6 find the solution of quadratic equation of one variable.
--【Source program】Example 4.7 calculate the transportation cost for the user.
--4.3 Self test questions
-Chapter 4 Self test questions
-5.1 While and Do-While Statement
--5.1 While and Do…while statement.mp4
--【Source program】example 5.1 Use while statement to find 1 + 2 + 3 + +100
--【Source program】example 5.2 using do while statement to find 1 + 2 + 3 + +100
--5.1 Self test questions
-5.2 For Statement
--【Source program】example 5.3 Use for loop to find 1 + 2 + 3 +100
--5.2 Self test questions
-5.3 Change the State of Loop Execution and Nested Loop
--5.3 Change the state of loop execution and nested loop .mp4
--【Source program】example 5.4 collecting charity donations
--【Source program】example 5.5 output a number between 100 and 200 that cannot be divided by 3.
--【Source program】multiplication table
--【Source program】example 5.6 Output the following 4*5 matrix.
--5.3 Self test questions
-5.4 Loop Structure Program example 1
--5.4 Loop structure program example 1.mp4
--5.4 Self test questions
-5.5 Loop Structure Program example 2
--5.5 Loop structure program example 2.mp4
--【Source program】example 5. Output the following figure.
--【Source program】example6. The problem of 100 chickens and 100 coins
--【Source program】example 7. Find the approximate value of PI
--5.5 Self test questions
-Chapter 5 Self test questions
-6.1 Definition, Reference and Initialization of One-Dimensional Arrays
--6.1 Definition, Reference of One-Dimensional Arrays.mp4
--6.1 Self test questions
-6.2 One-Dimensional Array Programming
--6.2 One-Dimensional Array Programming.mp4
--【Source program】example 1. Fibonacci sequence
--【Source program】example 2. Find the maximum value and the minimum value.
--【Source program】example 3 exchanging array elements in reverse order.
--【Source program】example 4. Bubble sorting.
--6.2 Self test questions
-6.3 Definition, Reference and Initialization of Two-Dimensional Arrays
--6.3 Definition, Reference of Two-Dimensional Arrays.mp4
--6.3 Self test questions
-6.4 Two-Dimensional Array Programming
--6.4 Two-Dimensional Array Programming.mp4
--【Source program】example 1. Get the average score of each subject.
--【Source program】Example 2. The elements of row and column of a 2D array are interchanged
--6.4 Self test questions
-6.5 Definition, initialization and input and output of character arrays
--6.5 Definition, initialization and input and output of character arrays .mp4
--【Source program】Example 6.6 Output a known string.
--【Source program】Example 6.7 Output a diamond.
--【Source program】Example 6.10 Sorting of strings.
--6.5 Self test questions
-6.6 String Processing Function
--6.6 String Processing Function.mp4
--6.6 Self test questions
-6.7 Character Array Programming
--6.7 Character Array Programming.mp4
--6.7 Self test questions
-Chapter 6 Self test questions
-7.1 Function Concept and How to Define and Call Functions
--7.1 Function Concept and How to Define and Call Functions.mp4
--7.1 Self test questions
-7.2 Data Transfer in Function Call, Call Procedure and Function Return Value
--7.2 Data Transfer in Function Call, Call Procedure and Function Return Value.mp4
--7.2 Self test questions
-7.3 Declarations of called functions and nested calls to functions
--7.3 Declarations of called functions and nested calls to functions .mp4
--【Source program】Example 7.4 use a function to find the sum of t
--7.3 Self test questions
-7.4 Recursive call to function
--7.4 Recursive call to function.mp4
--【Source program】Example 7.6. How old is the fifth student?
--【Source program】Example 7.7 Use recursion method to find n!
--7.4 Self test questions
-7.5 Array as function parameter (1)
--7.5 Array as function parameter (1).mp4
--【Source program】Example 7.10
--7.5 Self test questions
-7.6 Array as function parameter (2)
--7.6 Array as function parameter (2).mp4
--【Source program】Selection sorting.
--【Source program】Example 7.13 find the maximum of a 3×4 matrix.
--7.6 Self test questions
-7.7 Local and global variables, internal and external functions
--7.7 Local and global variables, internal and external functions.mp4
--【Source program】Example 7.14
--7.7 Self test questions
-7.8 The Survival Period of Variables and the Storage Mode of Local Variables
--7.8 The Survival Period of Variables and the Storage Mode of Local Variables.mp4
--【Source program】Example 7.17
--7.8 Self test questions
-7.9 Storage Categories of Global Variables
--7.9 Storage Categories of Global Variables.mp4
--7.9 Self test questions
-Chapter 7 Self test questions
-8.1 Pointer Concept, Definition and Reference of Pointer Variables
--8.1 Pointer Concept, Definition and Reference of Pointer Variables.mp4
--8.1 Self test questions
-8.2 Pointer variables as function parameters
--8.2 Pointer variables as function parameters.mp4
--【Source program】Example 8.3. Exchange two data with function call.
--8.2 Self test questions
-8.3 Pointer of array element, operation of pointer and reference of array element by pointer
--8.3 Pointer of array element, operation of pointer and reference of array element by pointer.mp4
--【Source program】Point to array elements with pointer variables.
--8.3 Self test questions
-8.4 Using Array Name as Function Parameter
--8.4 Using Array Name as Function Parameter.mp4
--【Source program】Store array elements in reverse order.
--8.4 Self test questions
-8.5 Reference to multidimensional arrays by pointers
--8.5 Reference to multidimensional arrays by pointers.mp4
--【Source program】Pointer variable pointing to one-dimensional array.
--8.5 Self test questions
-8.6 Referencing strings through pointers
--8.6 Referencing strings through pointers.mp4
--【Source program】Reference string by pointer.
--8.6 Self test questions
-8.7 Character pointer as function parameter
--8.7 Character pointer as function parameter.mp4
--【Source program】Character pointer as function parameter.
--8.7 Self test questions
-8.8 Pointer pointing to function
--8.8 Pointer pointing to function.mp4
--【Source program】Pointer variable pointing to the function.
--8.8 Self test questions
-8.9 Functions that return pointer values
--8.9 Functions that return pointer values.mp4
--【Source program】Intercept substring.
--8.9 Self test questions
-8.10 Pointer arrays and multiple pointers
--8.10 Pointer arrays and multiple pointers.mp4
--【Source program】Sorting of strings.
--8.10 Self test questions
-8.11 Dynamic memory allocation and pointer variables pointing to it
--8.11 Dynamic memory allocation and pointer variables pointing to it.mp4
--【Source program】Dynamic memory allocation.
--8.11 Self test questions
-Chapter 8 Self test questions
-9.1 Define and use structural variables
--9.1 Define and use structural variables.mp4
--【Source program】Structure variable
--9.1 Self test questions
-9.2 Using structure arrays
--9.2 Using structure arrays.mp4
--【Source program】Structure array
--9.2 Self test questions
-9.3 Structure pointer
--【Source program】Structure pointer
--9.3 Self test questions
-Chapter 9 Self test questions
-CodeBlocks Baidu online disk download address
-Final Exam
--final exam
