C语言变量的定义与使用

在C++中定义一个变量有2种方式int a=3; 和 int a(3);人认为，第一种是先调用了int的无参默认构造函数构造出对象a，然后再调用int的拷贝构造函数将3赋给a；第二种调用了int的构造函数，3作为构造函数的参数。这样分析起来，应该是第二种更好一些

C，语言的变量定义，这种定义的话，你应该去网上搜，而不是在这里问，而且连这个基础的定义你都不会，你还能干什么？

变量本质上就是代表一个"可操作性的存储空间",空间位置是确定的,但是里面放置什么值不确定.我们可通过变量名来访问"对应的存储空间",从而操纵这个"存储空间"存储的值.

定义a,b为整形变量

如果是51单片机的汇编的话，变量就是片内的寄存器或者片内RAM的某个单元。

不是很理解您问的问题，你是有否了解一点C基础。我只能猜测一下回答例：定义变量intNum;//定义了一个变量。int整型，是标准C++中的数据类型。Num是变量名。intNum1,Num2,Num3;//定义了3个整型变量，num1,num2,num3。（在同一行声明同一类型变量，变量名之间用逗号间隔，语句末尾仍然是以;封号结束）intNum=5;//定义一个int型变量Num并且将值初始化为5；例：输入输出操作如果是C++，那么首先包含头文件#include<iostream>usingnamespacestd;//然后在main函数里面写上：intNum1,Num2//定义变量cin>>Num1;//输入操作，对变量Num1进行写入。Num2=Num1;//将变量Num1的值赋给Num2。cout<<"Num2="<<Num2<<endl;//输出变量num2的值。（endl是回车换行。）

dima,basIntegera为variantb为integerdimaasInteger,basInteger定义a,b为整形变量DimaAsInteger-说明a为整型变量　　DimbAsString-说明b为可变长字符型变量　　DimcAsString~~10"说明c为长度是10个字符的固定长字符型变量　　Dimd(10)AsInteger-说明d为一维整型数组　　Dime()AsSingle-说明e为动态单精度变量　　StaticfAsInteger，说明f为静态整型变量　　ReDime(10)AsSingle-说明e为一维单精度数组　　GlobalhAsInteger-说明h为全局整型变量

不同的编程语言，规则是不一样的一般来说，定义变量的字符要求是“数字、字母、_”这三种而且变量的第一个字符不能是数字变量的长度不宜过长

float countdata=1.0;float是数据类型countdata是标识符，也就是变量名给定值中应该有小数，也可以不用带，系统自动给定

定义包括声明和使用，也有的定义就是声明。例如：int i;//声明(也有叫定义)i=2;//使用我把两个合起来的叫定义

情况一：符号变量必须要定义，定义之后才可以使用。如下面的例子，未定义就会出错。符号变量定义方法例如: sym x 或者 syms x ，两者有区别也有共同点。情况二：计算过程当中的存储数值的变量可以不必定义，随时需要，随时定义，但是有时候如果变量很多，那么最好提前声明，声明的时候，可以直接赋予0值，并且注释，这样方便以后区分，避免混淆。情况三：矩阵和向量对于矩阵一般都是需要定义的，定义好矩阵之后，才方便访问/修改矩阵的指定元素，矩阵声明（定义）的方法，常用的 就是声明为零矩阵zeros(M,N),或者单位矩阵ones(M,N),eye(M,N)等。

上面的答案都错了，系统分配给它的内存应该是成员中占内存量最大者所需的容量乘上所有成员的个数。 比如说一个struct type定义了一个int，一个char，一个float。 int4个字长，char1个字长，float4个字长。 而type的字长是12。

c语言的变量定义如下： 变量是内存或寄存器中用一个标识符命名的存储单元，可以用来存储一个特定类型的数据，并且数据的值在程序运行过程中可以进行修改。变量是一个标识符或者名称。为了方便，程序员在给变量命名时，会符合大多数人的习惯，基本可以望名知义，便于交流和维护。其次，变量是唯一确定的对应内存若干存储单元或者某个寄存器。

看你用的是哪种shell了对于bash，定义变量的形式是name="xxx"#定义了name变量，并将"xxx"字符串赋值给它如果要把name变量定义为环境变量，还需要在定义之后expor它对于csh，定义变量要用set，setname="xxx"csh定义环境变量要使用setenv命令

你是要用c语言写还是什么语言

要先给x赋值才行

全局变量的定义只能在函数外部，不能在函数内部。当要使用其他文件里的定义的全局变量时，可以用关键字extern，格式是[extern类型变量名;]希望对你有帮助。

判断一个变量有没有定义，如果没有定义，则现在就定义，这在判断一个变量是否由上一级Makefile export该变量，因为在大的软件中，一般由上层的Makefile export 相关的CC、CFLAGS等变量，而最后一级目录的Makefile不需要关心CC等的定义，但有时候不想编译整个工程，只想临时编译最低级的一个子目录，而此时子目录的Makefile就需要判断是否有该变量的定义，没有就需要定义。(另外，上级目录export 的变量不会覆盖下级目录定义的同名变量，想覆盖的话，使用: make -e )方法1: ifdef/ ifndefifndef $(CC) CC=../tools/bin/arm-linux-gccendif方法2: ifeqifeq($(CC), )CC=../tools/bin/arm-linux-gccendif方法3: ifeqifeq ("$(origin CROSS_COMPILE)", "undefined")CROSS_COMPILE=../../arm-linux-endif

VB可以在标准模块定义一个公用变量，这样就可以每一个过程中都可以使用。例如：DATA.bas在模块中新建一个通用模块,然后在新建模块里输入:Public 变量名 As 数据类型。举个例子，public number as integer在别的窗体中要引用number这个数，就写 DATA.number。标准模块（文件扩展名为 .BAS）是应用程序内其它模块访问的过程和声明的容器。它们可以包含变量、常数、类型、外部过程和全局过程的全局（在整个应用程序范围内有效的）声明或模块级声明。写入标准模块的代码不必绑在特定的应用程序上；如果不小心用名称引用窗体和控件，则在许多不同的应用程序中可以重用标准模块。所有模块使用的变量：为了使模块级的变量在其它模块中也有效，用 Public 关键字声明变量。公用变量中的值可用于应用程序的所有过程。和所有模块级变量一样，也在模块顶部的声明段来声明公用变量。Public 语句，在模块级别中使用，用于声明公用变量和分配存储空间。Public 语句示例：该示例在标准模块的模块级（通用部分）使用 Public 语句，来显式声明公用的变量，指如果没有使用 Option Private Module，则在所有应用程序的所有模块的所有过程中都可以使用的变量。变量的范围确定了能够知晓该变量存在的那部分代码。在一个过程内部声明变量时，只有过程内部的代码才能访问或改变那个变量的值；它有一个范围，对该过程来说是局部的。但是，有时需要使用具有更大范围的变量，例如这样一个变量，其值对于同一模块内的所有过程都有效，甚至对于整个应用程序的所有过程都有效。Visual Basic 允许在声明变量时指定它的范围。标准模块（文件扩展名为.BAS）是应用程序内其它模块访问的过程和声明的容器。所有模块使用的变量是为了使模块级的变量在其它模块中也有效，用 Public 关键字声明变量。

变量就是你的类中的用来暂时存储数据的东西定义方式为： 修饰符+变量类型+变量名= new 变量类型（）；如：private String a = new String();或直接赋值 private String a = "abc";但是a的值在你不断赋值的过程中是可以变化的。常量就是值不会发生变化的量，和变量是相对的，比如一个常量aprivate final String a = "abc";那么这个a只是不会改变的，这就是常量

定义一个变量 再去判断范围不就行了吗？

用指针+动态内存分配+自动扩充，如：int capacity=16,len=0;char *s;s=(char*)calloc(capacity,sizeof(char));//...//内存不够了，扩充if(len>=capacity){capacity*=2;s=(char*)realloc(s,capacity*sizeof(char));}//...

变量是指在程序的运行过程中随时可以发生变化的量。变量是程序中数据的临时存放场所。在代码中可以只使用一个变量，也可以使用多个变量，变量中可以存放单词、数值、日期以及属性。由于变量让你能够把程序中准备使用的每一段数据都赋给一个简短、易于记忆的名字，因此它们十分有用。变量可以保存程序运行时用户输入的数据（如使用InputBox函数在屏幕上显示一个对话框，然后把用户键入的文本保存到变量中）、特定运算的结果以及要在窗体上显示的一段数据等。简而言之，变量是用于跟踪几乎所有类型信息的简单工具。变量有两种类型：属性变量和用户自己建立的变量。当我们在窗体中设计用户界面时，vb6会自动为产生的对象(包括窗体本身)创建一组变量，即属性变量，并为每个变量设置其缺省值。这类变量可供我们直接使用，比如引用它或给它赋新值。用户也可以创建自己的变量，以便存放程序执行过程中的临时数据或结果数据等等

很简单的：int、float、double等定义数，总是有范围的啊，比如：int的范围在-32768-32767之间。还有专门的枚举类型----enum，定义后变量取值就在指定范围内，格式如下：enumfg{1,2,3,5,4,6};enumfgi;这样i变量就被限制在了上面数值之间。

这个如何定义具体的我也是不太清楚看看别人怎么说的吧希望可以帮到你

int float 然后可以给定义的变量负值

把const换成dim，变量要用dim进行定义，不能用const定义

Dim 变量名 as 类型

#define 试试吧

定义一个实型变量floatcountdata的方法如下：floatcountdata=1.0;其中：float是浮点型（小数点类型）数据类型，countdata是标识符，也就是变量名；

%matlab本身无法定义一个变量为正整数n=input("请输入一个正整数：");whilefix(n)~=n|n<0|n=0n=input("输入的不是正整数，请重新输入：")end使用说明：（1）变量名必须以字母或下划线打头，名字中间只能由字母、数字和下划线“_”组成；最后一个字符可以是类型说明符；（2）变量名的长度不得超过255个字符；（3）变量名在有效的范围内必须是唯一的。有效的范围就是引用变量可以被程序识别、使用的作用范围——例如一个过程、一个窗体等等。

AD

#define STR "abc"CString str = STR;这是你想要的吗？

定义一个变量就是说本来没有的你现在定义了一个出来而申明一个变量就是说系统本来有的 比如string　char 啊

正确的。在程序运行过程当中不断发生改变的量被称为变量。格式，类型标识符+空格+变量名，C规定，在使用变量之前，必须要先定义。定义变量就是事先跟C“打个招呼”。变量名可以根据程序的需要，由用户随便取。变量名必须是要以下划线或英文字母开头，而且不能与关键字同名，还不能含有特殊符号（比如说我们来个3ab的话，那么不符合，那么_3ab的话，就符合了，再比如我们来个main的话，那么不符合，main是个函数，它已经被C语言所使用了，+，-，*，/这些都是特殊字符）。

#include "stdio.h"struct Staff{ int ID; char name[20]; int age; float wage; char sex; char address[100];};void output(struct Staff* stf){ printf("Staff ID: %d ",stf->ID); printf("Staff name: %s ",stf->name); printf("Staff age: %d ",stf->age); printf("Staff wage: %f ",stf->wage); printf("Staff sex(M/W): %c ",stf->sex); printf("Staff address: %s ",stf->address);}void input(struct Staff* stf){ printf("Staff ID: "); scanf("%d",&(stf->ID) ); printf("Staff name: "); scanf("%s",&(stf->name) ); printf("Staff age: "); scanf("%d",&(stf->age) ); printf("Staff wage: "); scanf("%f",&(stf->wage) ); printf("Staff sex(M/W): "); scanf("%c",&(stf->sex) ); printf("Staff address: "); scanf("%s",&(stf->address) );}

注释怎么都是乱码呢？你复制到vc里之后把注释删除。没有说明语言种类，就用C编了 #include <stdio.h> #include <stdlib.h> #include <time.h>void Swap(int *a, int *b) { int swap; swap = *a; *a = *b; *b = swap; }void Array(int *Arr, int n) { int i = 0; int j = 0; //随机赋值 srand((int) time(0)); for(i = 0; i < n; i++) { Arr[i] = rand() % (100); } //冒泡排序 for(i = 0; i < n; i++) { for(j = i+1; j < n; j++) { if(Arr[i] < Arr[j])Swap(&(Arr[i]), &(Arr[j])); } } }int main() { int n = 0; //数组长度 int *Arr = NULL; printf("Please enter the lenth of array:"); scanf("%d", &n); //手动输入 Arr = (int*)malloc(sizeof(int) * n); Array(Arr, n); //输出结果 for(int i=0; i<n; i++) { printf("%d",Arr[i]); } free(Arr); return 0; }

你把intx,y;//x,y定义为局部变量这个语句放到程序开始，就是voidmain(){后面不是每个编译器都是必须在程序开始定义变量的，很多编译允许在使用的时候才定义变量。但keil就是一个要在程序开始定义变量的编译器。

就是定义这个变量继承于哪个类：比如string，int，bool 都有自己类的属性和赋值方式

int const a=7

不怎么了解

每个语言对变量的要求不一样的但基本上是不能使用大部分特殊字符,首字母不能是数字

B 变量的定义要逗号隔开C 字符要加单引号D 变量重复定义了

下面以整型变量为例介绍：#define BIT3 (0x1<<3)unsigned int flag;void set_bit3(void) //置位{ a |= BIT3;}void clear_bit3(void) //清零{ a &= ~ BIT3;}如果想要保留置位的结果，则需把flag声明为static即可。有问题，继续问，给分吧。

sbit FLAG=P3^1;

皆可

现象解释型、应用文、记叙文、和图表文章四种题型。这四种题型既是对四级作文的科学分类，又是对四级作文考点的高度概括。A现象段落模仿练习：当前校园中存在许多作弊的现象.Currently, college students in growing numbers are seeking to cheat in exams. According to a recent survey made by Mary Wang, head editor of the 21st Century, there are about % who had some cheating behaviors at college, even in College English Test. Such an phenomenon has caused wide public concern.

2008年12月四级写作范文 一 1.一次性塑料袋曾被广泛的使用 2.造成的问题 3.限制使用的意义 Disposable plastic bags were once widely used in China. When we went shopping at supermarkets and departments stores, shopping assistants often provided free plastic bags for our convenience. For a while, life without them seemed unimaginable for most of us. However, disposable plastic bags do bring severe damage to our environment. Costumers usually threw them away after use, and because they are thin and hard to decompose, these plastic products will exist for a long time. This is an immediate threat to our earth and water. Nowadays, the government has passed relevant regulations for limiting the use of disposable plastic bags: they are not free any more. In some shopping places, in order to invoke the public awareness of environmental protection, plastic bags are offered in a much higher price. As a result, people are changing their behavior: paper and clothing bags that vanished for a long time come back to our daily life. It is true that by limiting its usage, everyone in this society contributes some effort to the improvement of the environment. 二 · Limiting the Use of Disposal Bags ·These days disposal products often hit the headlines of newspapers and have been brought into focus of the public. Indeed, it is widely accepted that they have gained increasing popularity among people in all walks of life. Taking a look around you, you can find examples too numerous to list: When you walk on the street, you can see plastic bags flying over your head; When you ramble along the river, you can find plastic bottles floating on the water; When you stroll in the park with your lover, you can notice waste paper thrown everywhere. · Among the most important reasons often cited by people is the quickening pace of modern life. They are often too busy to wash dirty dishes or glasses, as a result they can do nothing but use disposal products. Also playing a part is the improvement of people"s life. As a result of the policy of opening and reform, an increasing number of people are much richer than before and can afford disposal products. (原因) · Admittedly, they might benefit us in a short term. Unfortunately, they will do us harm in more than one way. The major harm is (that) they are sure to pollute the environment. To make matters worse, they are likely to have potential harm to public health. To illustrate this point, I can think of no better example than HP, the river through S. As a result of disposal products in it, the water has caused some diseases in the local people. (影响) · To sum up, for the factors mentioned before, we can safely reach the conclusion that the prevalence of disposale products is bound to cause a chain of undesirable effects. In view of the present situation, it is high time that the government tried every means to protect the environment. Only in this way, can we have a bright future. 2008年12月英语四级写作范文(昂立版) 昂立四级范文 1.一次性塑料袋的使用 2.使用一次性塑料袋带来的问题 3.限制使用一次性塑料袋的意义 一Disposable Plastic Bags Nowadays we may find ourselves surrounded by a sea of disposable plastic bags. And recently the problems of using disposable plastic bags have been brought into people"s focus. First of all, the use of disposable plastic bags causes irreversible harm to our environment. As these bags are not biodegradable, they are blocking the drainage system and causing water pollution. What"s more, customers using disposable plastic bags may think that they are of great convenience. But what they don"t quite realize is that there will be remarkable negative impact on our health. And sometimes careless disposal of these bags may even poison some innocent animals. In view of the severity of this issue, effective measures have been taken in our country. There has been a strict limit on the using of disposable plastic bags in supermarkets, which not only enhances people"s awareness on environmental protection but also cuts down the cost of the running of supermarkets. 二 1.一次性塑料袋的使用 2.使用一次性塑料袋带来的问题 3.限制使用一次性塑料袋的意义 Disposable Plastic Bags Nowadays we may find ourselves surrounded by a sea of disposable plastic bags . And recently the problems of using disposable plastic bags have been brought into people"s focus. First of all, the use of disposable plastic bags causes irreversible harm to our environment. As these bags are not biodegradable, they are blocking the drainage system and causing water pollution. What"s more, customers using disposable plastic bags may think that they are of great convenience. But what they don"t quite realize is that there will be remarkable negative impact on our health. And sometimes careless disposal of these bags may even poison some innocent animals. In view of the severity of this issue, effective measures have been taken in our country. There has been a strict limit on the using of disposable plastic bags in supermarkets, which not only enhances people"s awareness on environmental protection but also cuts down the cost of the running of supermarkets. 08.12.20 英语四级作文真题范文(恩波版) Limiting the Use of Disposable Plastic Bag Plastic bags have been an indispensable part of our daily life for it brings us much convenience. We are so dependent upon plastic bags that use of them is ever increasing. Despite the convenience it brought to people, it also caused a lot of problems amony which the environmental pollution was the biggest concern. Plastic bags not only affect the beautifulness of our environment, but also do harm to our health, because they are made of some kind of chemical material which can not be discomposed. Therefore, limiting the use of disposable plastic bags is of great significance. First of all, this policy can reduce pollution and save a lot of resource at the same time; secondly, it contributes a lot of resource at the same time; secondly, it contributes a lot to a more beautiful living environment; last but not least, it can also create a healthier environment for people. In short, we should do our best to limit the use of plastic bags for ourselves and for the next generation. 08.12.20 英语四级作文范文(交大外院) 1. 一次性塑料袋的使用 2. 使用一次性塑料袋带来的问题 3. 限制使用一次性塑料袋的意义 For many years we have been using disposal plastic bags when we are shopping on the market, and most often these bags are offered by the shops for free. This, undoubtedly, has brought us great convenience in our daily life. However, its disadvantages are also very apparent, and I"ll just venture to explore two aspects. For one thing, the plastic bags are mostly indecomposable in the natural state so that with the increasing use of these bags, it will not only seriously bring about the so-called “white pollution” to the environment, it can also cost us a lot to have them decompose completely so as to minimize their damage to the environment. For another, the production of plastic bags are often not strictly supervised, so a large proportion of the bags don"t meet the requirements for healthy products, which means the more we use them, the more likely we are to suffer in health. The negative effects of the plastic bags are far serious than what I"ve mentioned above, so it"s high time the government issued strict laws and measures to stop using the bags. By so doing, we can save a lot of money from producing these bags as well as return a cleaner earth to ourselves and the later generations.

英语四级写作题目类型有：现象阐释型。这类作文多为提纲式作文或图表式作文。这类问题要求考生对某一种社会现象进行解释，分析其产生的原因，并对其进行评论。1、对比选择型。这类作文多为提纲式作文，议论文体裁。通常首先讨论两种相反的观点，或者分析一种社会现象的利弊，然后给出自己的观点。2、观点论证型。这类作文通常是提纲式的议论文或图片式的作文，通常是围绕某一事物或观点进行论证;有时以一个热门话题或某种现象作为讨论的对象，要求考生给出自己的看法，并加以论证。3.问题解决型。这类作文一般是提纲作文，多为议论文。通常从一个需要解决的问题开始，然后要求考生就该问题给出解决方案。英语四级作文考高分的技巧如下：1、保证基本正确。四级作文得不到高分较大的问题不是考生写得太简单，而是犯了太多严重的错误。基础一般的考生即使能正确使用小学或高中的词汇和句型，也还是能得到及格分数。2、丰富多变。基础好的考生要想在四级作文中取得高分，就必须做到丰富多变，丰富多变主要体现在词汇和句型两方面。同一词语在一个句子、一个段落甚至是一篇文章中，比较好不要重复，应尽量使用同、近义词替换(除非关键字不能被替换)。3、长短句结合。四级作文如果量化成句数，需要写10句左右。全文应以短句为基础，长句和短句相结合。