## C++ Standard Library And Expressions

Standard library contains files storing standard functions(I/O functions, mathematical functions, string functions, character functions etc.). These are some files known as header files.

The C ++ standard library contains a lot of header files. The file usually has an .h extension. These header files contain a set of functions, which are grouped together based on their functionality. They perform depending on the nature of the operation.

Header File | Description |
---|---|

stdio.h | The file defines types and macros that are needed for I/O packages. |

string.h | The file declares various string manipulation and memory mainpulation. |

math.h | The file declares various math function and math error handlers. |

stdlib.h | The file declares several commonly used routines like conversion routines, search routines etc. |

iostream.h | The file declares basic c++ stream I/O routines. |

iomanip.h | The file declares basic c++ stream I/O manipulators and contains macros for creating parameter manipulator. |

We can add header files in the program by using the extension :

**Syntax :**#include<header file>

**Example :**#include<iostream.h>

## Expressions

The expression in C++ is combination of tokens.

**Arithmetic Expression :**

There are two types of arithmetic expression pure integer expression and pure real expression. Mixed expressions are also commonly used, which is a mixture of both pure integer expressions and pure real expressions.

**Pure Integer Expression :**

This type of expression when an integer is formed by a combination of integer constant or integer variables using integer arithmetic operators.

The following are valid pure integer expression :

**Example :**

const count = 30;

int I,J,K,L,M;

**Pure Real Expression :**

This type of expression when an integer is formed by a combination of real constant or real variables using real arithmetic operators.

The following are valid pure real expression :

**Example :**

const bal = 200.53;

float num, value;

double fout, count;

## Exercise:-

1. Which header file is used during math function and math error handlers?

View Answer

2. Which of the following keyword is used to include the header file?

View Answer

## Program :-

Write a program to read coordinates of two points and calculate the distance between them.

#include <bits/stdc++.h> using namespace std; // This will calculate distance float distance(int a, int b, int c, int d) { // Logic to Calculating distance return sqrt(pow(c - a, 2) + pow(d - b, 2) * 1.0); } // Main Code int main() { cout << distance(5, 6, 6, 5); return 0; }

**Output :**

1.41421

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