IC003 – Variables in C++

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Variables are like a warehouse, representing a storage unit, and their values can change during the execution of a program.

In C++, the format for defining a variable is as follows:

Format: data type variable_name1, variable_name2, ……, variable_n

Function: Allocates n spaces of the specified data type in computer memory, named variable_name1, variable_name2, ……, variable_n.

For example: int a, which allocates a space of integer data type with the variable name a in computer memory.

Common variable types include integer int, floating-point float, and character char, etc.

Exercise Program:

#include <iostream>
using namespace std;
int main(){
    int a,b;
    a=2;
    b=5;
    cout<<"a="<<a<<" "
        <<"b="<<b<<endl;
    //endl means new line
    b=8;
    cout<<"a="<<a<<" "
        <<"b="<<b<<endl;
}

Debugging Results:

a=2 b=5

a=2 b=8

After a variable is defined, the system allocates a storage space for it in the computer. When a variable is used in the program, the system will store or retrieve data in the corresponding memory. This operation is called variable access.

Variable Naming Rules:

A program may need to use multiple variables, and to distinguish between them, each variable must be given a name, known as the variable name. The naming rules for variables in C++ are as follows:

(1) Variable names may only contain letters, numbers, or underscores;

(2) The first character of a variable name cannot be a number and cannot contain other characters;

(3) Variable names cannot be C++ keywords, such as main, etc.

(4) Variables must be “defined before use”; variable names are case-sensitive. It is recommended that variable names do not exceed 8 characters in length.

Exercises:

1. Read the program and write the final running result on the line below.

#include <iostream>
using namespace std;
int main(){
    int a;
    a=10;
    a=20;
    a=30;
    a=40;
    a=50;
    cout<<a<<endl;
}

Running Result:________________

2. Store the real number 5.6 in the computer memory variable b and output it.

1.IC002 – C++ Writing Hello World2.CSP-J/S Examination3.Informatics Competition 001 – Dev C++ Installation

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