C++ Variables

C++ Variables

ຕົວປ່ຽນຂອງພາສາ C++

C++ Variables

Variables are containers for storing data values.

In C++, there are different types of variables (defined with different keywords), for example:

Multiple Choice

ຕົວປ່ຽນແມ່ນຫຍັງ

• ຂໍ້ມູນ

• ບ່ອນຈັດເກັບຂໍ້ມູນ

• ປະເພດຂໍ້ມູນ

• ຈຳນວນ

C++ Variables

• int - stores integers (whole numbers), without decimals, such as 123 or -123

• double - stores floating point numbers, with decimals, such as 19.99 or -19.99

• char - stores single characters, such as 'a' or 'B'. Char values are surrounded by single quotes

• string - stores text, such as "Hello World". String values are surrounded by double quotes

• bool - stores values with two states: true or false

Multiple Choice

ຂໍ້ໃດຕໍ່ໄປນີ້ແມ່ນປະເພດຂອງຕົວປ່ຽນຂອງພາສາ C++

• google

• data

• type

• string

Declaring (Creating) Variables

To create a variable, you must specify the type and assign it a value:

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ຕົວປ່ຽນພາສາອັງກິດຂຽນແບບໃດ

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ຈົ່ງຂຽນຕົວປ່ຽນທີ່ຕົວເອງຮູ້ຈັກມາ 1 ຕົວປ່ຽນ

Syntax variable C++

Where type is one of C++ types (such as int), and variable is the name of the variable (such as x or myName). The equal sign is used to assign values to the variable.

Create a variable called myNum of type int and assign it the value 15:

Multiple Choice

ຂໍ້ໃດຕໍ່ໄປນີ້ແມ່ນການສ້າງຕົວປ່ຽນທີ່ຖືກຕ້ອງ

• int a=50;

• int a=7

• int a="a"

• int a="a";

Syntax Variables

You can also declare a variable without assigning the value, and assign the value later:

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ໃຫ້ສ້າງຕົວປ່ຽນ ປະເພດຕົວເລກ ແລະ ຕັ້ງຊື່ວ່າ Mydata ໂດຍບໍ່ຕ້ອງກຳນົດຄ່າໃຫ້ກັບຕົວປ່ຽນ

Syntax Variables

Note that if you assign a new value to an existing variable, it will overwrite the previous value:

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Other Types

• int myNum = 5;               // Integer (whole number without decimals)

• double myFloatNum = 5.99;    // Floating point number

• char myLetter = 'D';         // Character

• string myText = "Hello";     // String (text)

• bool myBoolean = true;       // Boolean (true or false)

Multiple Choice

ຂໍ້ໃດຕໍ່ໄປນີ້ແມ່ນການກຳນົດ ຄ່າໃຫ້ກັບຕົວປ່ຽນ ທີ່ ບໍ່ຖືຕ້ອງ

• int a=50;

• double b=55.6;

• bool a=50;

• string a="love";

C++ Declare Multiple Variables

To declare more than one variable of the same type ( , ) use a comma-separated list:

int x = 5, y = 6, z = 50;

cout << x + y + z;

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ຈົ່ງສ້າງຕົວປ່ຽນປະເພດ string ຂື້ນມາ 3 ຕົວປ່ຽນຄື: name,surname,nickname

C++ Identifiers

All C++ variables must be identified with unique names.

These unique names are called identifiers.

Identifiers can be short names (like x and y) or more descriptive names (age, sum, totalVolume).

Note: It is recommended to use descriptive names in order to create understandable and maintainable code:

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ຂໍ້ໃດຕໍ່ໄປນີ້ເປັນການ ຕັ້ງຊື່ຕົວປ່ຽນທີ່ ຖືກຕ້ອງ

• name surname

• int

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C++ Identifiers

how to create Variables is very good

C++ Identifiers

• Names can contain letters, digits and underscores

• Names must begin with a letter or an underscore (_)

• Names are case sensitive (myVar and myvar are different variables)

• Names cannot contain whitespaces or special characters like !, #, %, etc.

• Reserved words (like C++ keywords, such as int) cannot be used as names

Multiple Select

ຂໍ້ໃດຕໍ່ໄປນີ້ເປັນການ ຕັ້ງຊື່ຕົວປ່ຽນທີ່ ບໍ່ຖືກຕ້ອງ

• name surname

• _year

• #data

• sum

C++ Constants

When you do not want others (or yourself) to override existing variable values, use the const keyword (this will declare the variable as "constant", which means unchangeable and read-only):

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ໃຫ້ຂຽນຄຳສັ່ງ ກຳນົດຄ່າຄົງທີ່ ໃຫ້ກັບຕົວປ່ຽນ

Poll

ຫົວຂໍ້ໃດຕໍ່ໄປນີ້ ຍັງບໍ່ທັນເຂົ້າໃຈດີ ຫຼື ທີ່ຄິດວ່າຍາກ

• C++ Variables

• C++ Declare Multiple Variables

• C++ Identifiers

• C++ Constants