5.2 for statement.mp4慕课视频播放-C Programming-MOOC慕课视频教程-柠檬大学

大家好

我是云南大学信息学院丁海燕老师

欢迎走进C语言程序设计课堂

今天我们讲解for语句

在C语言

提供的4种不同的循环语句中

for语句最简洁

最灵活

不仅可用于循环次数已经确定的情况

也可用于循环次数虽不确定

但给出了循环继续条件的情况

下面来看例5.3

for语句

用for循环求1+2+3+…100

流程图如图所示

{int n, sum=0; //

首先将累加器sum初始化为0

for(n=1; n<=100; n++)

sum += n; //

实现累加

printf输出结果

程序运行结果如下

sum=5050

for语句

不仅可以用于

循环次数已经确定的情况

还可以用于循环次数不确定

而只给出循环结束条件的情况

for语句完全可以代替while语句

下面程序循环输出1到100

for (i=1;i<=100;i++)

{ printf("%d ", i );

for语句的一般形式为for

(表达式1；表达式2；表达式3)

语句

表达式1

用来设置初始条件

只执行一次

可以为零个

一个或多个变量设置初值

表达式2

为循环条件表达式

用来判定是否继续循环

在每次执行循环体前

先执行此表达式

决定是否继续执行循环

表达式2一般是关系表达式

或逻辑表达式

但也可以是数值表达式

或字符表达式

只要其值为非0

就执行循环体

表达式3

作为循环的调整器

例如使循环变量增值

它是在执行完循环体后才进行的

for语句的执行过程如下

一

先求解表达式1

二

求解表达式2

若其值为真

执行循环体

然后执行下面第3步

若为假

则结束循环

转到第5步

三

求解表达式3

四

转回上面步骤2

继续执行

五

循环结束

执行for语句下面的一个语句

for语句的流程图和N-S结构图

如图所示

for(i=1;i<=100;i++)

sum=sum+i

等价于

i=1

while(i<=100)

{ sum=sum+i

i++

}

可见用for语句更简单、方便

for(表达式1；表达式2 ；表达式3)

语句

所有用 while 语句实现的循环

都可以用for 语句实现

等价于

表达式1；

while （表达式2）

{ 语句

表达式3

}

在for语句中

表达式1

当中的1个

2个或3个表达式

均可以省略

但分号不能省略

一

表达式1、2、3全省略

即for

( ; ; )

就等同于while (1)

会无限循环

也就是死循环

二

省略表达式1和表达式3

即

for

（；表达式2；）

就等同于while

（表达式2 ）

三

省略表达式2

即

for

（表达式1；；表达式3）

就等同于

表达式1; while(1)

｛…表达式3;｝

注意

在省略某个表达式时

应在适当位置

进行循环控制的必要操作

以保证循环的正确执行

表达式1

可以是设置循环变量初值的

赋值表达式

也可以与循环变量无关的其他表达式

例如

for (sum=0 ; i<=100; i++)

sum=sum+i

此时表达式1 sum=0

与循环变量无关

表达式1和表达式3

可以是一个简单的表达式

也可以是逗号表达式

即包含一个以上简单表达式

中间用逗号分隔

例如

for(sum=0,i=1 ; i<=100; i++)

sum=sum+i

例如

for(i=0,j=100

; i<=j; i++,j-- )

k=i+j

下面分析以下两个例子

一

for(i=0;

(c=getchar())!=’ ′;

i+=c)

在表达式2中

先从终端接收一个字符赋给c

然后判断此赋值表达式的值

是否不等于’ ’换行符

如果不等于’ ’

就执行循环体

它的作用是不断输入字符

将它们的ASCII码相加

直到输入一个“换行”符为止

此for语句的循环体为空语句

把本来要在循环体内处理的内容

放在表达式3中

作用是一样的

可见for语句功能强

可以在表达式中

完成本来应在循环体内完成的操作

二

for( ; (c=getchar())!=’ ’; )

printf(″%c″，c);

for语句中只有表达式2

而无表达式1和表达式3

其作用

是每读入一个字符后

立即输出该字符

直到输入一个“换行”为止

下面熟悉几个循环语句

while (!x) x++;

当 x=0 时

执行循环体x++;

while ((c=getchar( )) != ' ') n=n+1;

n 称为计数器

作用是统计输入字符的个数

while (num++<=2)

printf("%d ",num);

循环体是空语句

退出循环后输出num的值

do x*=-3

while(x>5)

先执行循环体x*=-3

再判断条件(x>5)

for (n=0; n<26; n++) printf("%c ", n+'A')

作用是输出26个大写字母

for (sum=0, i=1; i<=100

sum=sum+i, i+=2)

作用是计算100以内的奇数和

几种循环语句的比较如下

while 和for先判断循环条件后

执行循环体

do-while语句先执行循环体后

判断循环条件

while语句多用于循环次数不定的情况

do-while语句多用于

至少要运行一次的情况

for语句多用于要赋初值

或循环次数固定的情况

好了

同学们

for语句我们就学到这儿

下节课再见

C Programming课程列表：

Chapter 1 Introduction

-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

--Discussion unit

--【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

--Discussion unit

--Running steps of C source program in CodeBlocks

--1.3 Self test questions

-Course references

-chapter 1 Self-Test

Chapter 2 Algorithm

-2.1 The Concept and Description of Algorithms

--2.1 The Concept and Description of Algorithms.mp4

--Discussion unit

--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

--Discussion unit

--2.2 Self test questions

-Chapter 2 Self test questions

Chapter 3 Programming in C

-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

--Discussion unit

--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

--Discussion unit

--【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

Chapter 4 Selection Structure

-4.1 Relational operators, logical operators, and if statements

--4.1 Relational operators, logical operators, and if statements.mp4

--Discussion unit

--【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

--4.2 Switch Statement .mp4

--Discussion unit

--【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

Chapter 5 Loop Structure

-5.1 While and Do-While Statement

--5.1 While and Do…while statement.mp4

--Discussion unit

--【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

--5.2 for statement.mp4

--【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

--【Source program】example 1

--【Source program】example 2

--【Source program】example 3

--【Source program】 Example 4

--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

Chapter 6 Batch Data Processing with Array

-6.1 Definition, Reference and Initialization of One-Dimensional Arrays

--6.1 Definition, Reference of One-Dimensional Arrays.mp4

--Discussion unit

--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

--Discussion unit

--【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

Chapter 7 Modular Programming with Functions

-7.1 Function Concept and How to Define and Call Functions

--7.1 Function Concept and How to Define and Call Functions.mp4

--【Source program】Example 7.1

--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

--Discussion unit

--【Source program】Example 7.2

--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

--Discussion unit

--【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

Chapter 8 Pointer

-8.1 Pointer Concept, Definition and Reference of Pointer Variables

--8.1 Pointer Concept, Definition and Reference of Pointer Variables.mp4

--【Source program】Example 8.1

--8.1 Self test questions

--Discussion unit

-8.2 Pointer variables as function parameters

--8.2 Pointer variables as function parameters.mp4

--Discussion unit

--【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

--Discussion unit

--【Source program】Dynamic memory allocation.

--8.11 Self test questions

-Chapter 8 Self test questions

Chapter 9 Structure

-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

--Discussion unit

--【Source program】Structure array

--9.2 Self test questions

-9.3 Structure pointer

--9.3 Structure pointer.mp4

--【Source program】Structure pointer

--9.3 Self test questions

-Chapter 9 Self test questions

CodeBlocks Baidu online disk download

-CodeBlocks Baidu online disk download address

Final Exam

-Final Exam

--final exam

5.2 for statement.mp4在线视频

5.2 for statement.mp4课程教案、知识点、字幕

C Programming课程列表：

Chapter 1 Introduction

Chapter 2 Algorithm

Chapter 3 Programming in C

Chapter 4 Selection Structure

Chapter 5 Loop Structure

Chapter 6 Batch Data Processing with Array

Chapter 7 Modular Programming with Functions

Chapter 8 Pointer

Chapter 9 Structure

CodeBlocks Baidu online disk download

Final Exam

5.2 for statement.mp4笔记与讨论

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