Introduction to c++
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1. Identifiers in C++ are used to name variables, functions, and other user-defined items. They can include letters, digits, and underscores but not special characters or keywords. 2. There are two types of identifiers: standard identifiers which have special predefined meaning, and user-defined identifiers which are defined by the programmer. 3. Data types in C++ include built-in types like int and char, user-defined types like classes and structures, and derived types like arrays and pointers.
![Derived Data Types:
The data-types that are derived from the primitive or built-in data types are referred to as Derived Data
Types.
1. Function: A function is a block of code or program-segment that is defined to perform a specific well-
defined task.
Syntax:
FunctionType FunctionName(parameters)
2. Array: An array is a collection of items stored at continuous memory locations. The idea of array is to
represent many instances in one variable.
Syntax:
DataType ArrayName[size_of_array];
3. Pointers: Pointers are symbolic representation of addresses.
Syntax:
datatype *var_name;
4. Reference: When a variable is declared as reference, it becomes an alternative name for an existing
variable.](https://image.slidesharecdn.com/dawooduniversityofengineering-200403082220/85/Introduction-to-c-7-320.jpg)
Introduction to c++
- 1. DAWOOD UNIVERSITY OF ENGINEERING & TECHNOLOGY Computer Systems Engineering
- 2. Identifiers: • Identifier is a name used to identify a variable, function or any other user- defined item. • It is an arbitrarily long sequence of digits (0 to 9). • Lower case (a to z) & upper case (A to Z). • Identifier should not be keywords. • Special characters are not allowed except underscore (_). • E.g. _ab1, ab_, etc.
- 3. There are two types of identifier. 1. standard identifiers. 2. user- defined identifiers. 1. Standard identifiers: A type of identifier that has special meaning in c++. C++ cannot use a standard identifier for the original purpose if it is re-defined. * Cout & cin are the examples of standard identifier. 2. User-Defined Identifiers: The type of identifier that is defined by the programmer to access memory location. * E.g. subject, age, marks, etc.
- 4. They are defined those variables which have special meaning and are pre- defined in the c++ libraries. * Keywords also known as reserved words. * There are 63 keywords in c++ library. * They are always written in lowercase. * They cannot be used for another purpose like identifiers. E.g. if, else, limit, delete, public, namespace, new, using, etc. KEYWORDS:
- 5. Data types: • Data types define the type of data a variable can hold, for example an integer variable can hold integer data, a character type variable can hold character data etc. • Data types in C++ are categorized in three groups: 1. Built-in data type. 2. user-defined data type. 3. Derive data type.
- 6. Built-in data type or Primitive Data Types: These data types are built-in or predefined data types and can be used directly by the user to declare variables. 1. char: For characters. Size 1 byte. char ch = 'A'; 2. int: For integers. Size 2 bytes. int num = 100; 3. float: For single precision floating point. Size 4 bytes. float num = 123.78987; 4. double: For double precision floating point. Size 8 bytes. double num = 10098.98899; 5. bool: For booleans, true or false. bool b = true; 6. wchar_t: Wide Character. This should be avoided because its size is implementation defined and not reliable.
- 7. Derived Data Types: The data-types that are derived from the primitive or built-in data types are referred to as Derived Data Types. 1. Function: A function is a block of code or program-segment that is defined to perform a specific well- defined task. Syntax: FunctionType FunctionName(parameters) 2. Array: An array is a collection of items stored at continuous memory locations. The idea of array is to represent many instances in one variable. Syntax: DataType ArrayName[size_of_array]; 3. Pointers: Pointers are symbolic representation of addresses. Syntax: datatype *var_name; 4. Reference: When a variable is declared as reference, it becomes an alternative name for an existing variable.
- 8. Abstract or User-Defined Data Types: These data types are defined by user itself. Like, defining a class in C++ or a structure. 1. Class: The building block of C++ that leads to Object-Oriented programming is a Class. 2. Structures: A structure creates a data type that can be used to group items of possibly different types into a single type. 3. Union: In union, all members share the same memory location. 4. Enumeration: It is mainly used to assign names to integral constants, the names make a program easy to read and maintain.