Detailed explanation of C++ function library: extension and connotation of system functions

The C function library provides predefined functions and classes that extend the functionality of C and simplify programming, giving applications additional capabilities. These function libraries cover a variety of tasks from file operations to system calls. A common use case is to use the fstream function library to implement file reading and writing, for example, reading and displaying the contents of a text file.

Detailed explanation of C function library: extension and connotation of system functions

C function library is a set of predefined functions and classes , they offer a wide range of features that greatly simplify programming and increase productivity. These libraries give applications greater capabilities beyond their basic functionality, enabling them to perform a variety of system-level tasks.

Function extension of the C function library

The C function library extends the built-in functions of the C language and provides ready-to-use solutions for the following tasks:

• File and stream operations (ifstream, ofstream)
• Memory operations (new, delete)
• Input/ Output (cin, cout)
• Error handling (exception)
• Mathematics and trigonometric functions (math.h)
• Time and date operations (chrono)
• Containers and algorithms (vector, algorithm)

These libraries provide standardization A portable, portable way to perform these tasks, simplifying code writing and maintenance.

The connotation of C function library

In addition to extending language functions, the C function library also provides access to the underlying mechanisms of the system, such as:

• System call (sys/syscall.h)
• Process management (fork, exec)
• Multi-thread programming ( pthread)
• Network Programming (socket)

These function libraries allow programmers to interact directly with the operating system and hardware to perform advanced system programming tasks .

Practical case: file reading and writing

Let us use the fstream function library to write a program to read and display the contents of the file:

#include <fstream>
#include <iostream>

using namespace std;

int main() {
  // 打开文件
  ifstream fin("input.txt");

  // 检查是否成功打开
  if (!fin.is_open()) {
    cout << "Error opening file" << endl;
    return -1;
  }

  // 读取文件内容
  string line;
  while (getline(fin, line)) {
    cout << line << endl;
  }

  // 关闭文件
  fin.close();

  return 0;
}

This program uses the ifstream function library to open a text file, read its contents, and display it on the console.

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