Cprogramming 简明教程

C Language - Overview

C 是一种通用高级语言，最初由 Dennis M. Ritchie 开发，用于在贝尔实验室开发 UNIX 操作系统。C 最初于 1972 年在 DEC PDP-11 计算机上首次实现。

C is a general−purpose, high−level language that was originally developed by Dennis M. Ritchie to develop the UNIX operating system at Bell Labs. C was originally first implemented on the DEC PDP-11 computer in 1972.

1978 年，Brian Kernighan 和 Dennis Ritchie 制作了 C 的第一个公开描述，现称为 K&R 标准。

In 1978, Brian Kernighan and Dennis Ritchie produced the first publicly available description of C, now known as the K&R standard.

UNIX 操作系统、C 编译器以及基本上所有 UNIX 应用程序都是用 C 编写的。C 因各种原因现已成为一种广泛使用的专业语言 −

The UNIX operating system, the C compiler, and essentially all UNIX application programs have been written in C. C has now become a widely used professional language for various reasons −

  1. Easy to learn

  2. Structured language

  3. It produces efficient programs

  4. It can handle low−level activities

  5. It can be compiled on a variety of computer platforms

Facts about C

  1. C was invented to write an operating system called UNIX.

  2. C is a successor of B language which was introduced around the early 1970s.

  3. The language was formalized in 1988 by the American National Standard Institute (ANSI).

  4. The UNIX OS was totally written in C.

  5. Today C is the most widely used and popular System Programming Language.

  6. Most of the state-of-the-art software have been implemented using C.

  7. Today’s most popular Linux OS and RDBMS MySQL have been written in C.

Why Use C Language?

C最初用于系统开发工作，尤其是构成操作系统的程序。C被采纳为一种系统开发语言，因为它产生的代码运行速度几乎与汇编语言编写的代码一样快。

C was initially used for system development work, particularly the programs that make-up the operating system. C was adopted as a system development language because it produces code that runs nearly as fast as the code written in assembly language.

C的使用的一些示例可能是−

Some examples of the use of C might be −

  1. Operating Systems

  2. Language Compilers

  3. Assemblers

  4. Text Editors

  5. Print Spoolers

  6. Network Drivers

  7. Modern Programs

  8. Databases

  9. Language Interpreters

  10. Utilities

C涵盖了编程的所有基本概念。这是一个基础或母语言来学习面向对象的编程语言，如 C 、 Java 、 .Net 等。许多现代编程语言，如C、Java和 Python 都借鉴了C的语法和概念。

C covers all the basic concepts of programming. It’s a base or mother programming language to learn object−oriented programming like C, Java, .Net, etc. Many modern programming languages such as C, Java, and Python have borrowed syntax and concepts from C.

它提供了对硬件的精细控制，使其高效。因此，C通常用于开发系统级程序，如设计 Operating Systems 、操作系统内核等，也用于开发文本编辑器、编译器、网络驱动程序等应用程序。

It provides fine-grained control over hardware, making it highly efficient. As a result, C is commonly used to develop system−level programs, like designing Operating Systems, OS kernels, etc., and also used to develop applications like Text Editors, Compilers, Network Drivers, etc.

C程序是可移植的；因此，它们可以在不同的平台上运行，而无需进行重大的修改。

C programs are portable; hence they can run on different platforms without significant modifications.

在编程史上，C作为一种基础编程语言发挥了关键作用。然而，与更现代的语言相比，它在应用程序开发方面的受欢迎程度有所下降。这可能归因于它的低级特性以及存在更高层次的语言，这些语言提供了更丰富的预先存在的抽象和能力。尽管如此，在诸如最优性能、系统资源的细致管理以及对可移植性的迫切需要等因素至关重要的领域中，C编程语言仍然不可或缺。

C has played a pivotal role as a fundamental programming language over the course of programming history. However, its popularity for application development has somewhat diminished in comparison to more contemporary languages. This may be attributed to its low−level characteristics and the existence of higher−level languages that offer a greater abundance of pre−existing abstractions and capabilities. Nevertheless, the use of the programming language C remains indispensable in domains where factors such as optimal performance, meticulous management of system resources, and the imperative need for portability hold utmost significance.

Advantages of C Language

以下是C语言的优点−

The following are the advantages of C language −

  1. Efficiency and speed − C is known for being high−performing and efficient. It can let you work with memory at a low level, as well as allow direct access to hardware, making it ideal for applications requiring speed and economical resource use.

  2. Portable − C programs can be compiled and executed on different platforms with minimal or no modifications. This portability is due to the fact that the language has been standardized and compilers are available for use on various operating systems globally.

  3. Close to Hardware − C allows direct manipulation of hardware through the use of pointers and low−level operations. This makes it suitable for system programming and developing applications that require fine-grained control over hardware resources.

  4. Standard Libraries − For common tasks such as input/output operations, string manipulation, and mathematical computations, C comes with a large standard library which helps developers write code more efficiently by leveraging pre−built functions.

  5. Structured Programming − C helps to organize code into modular and easy−to−understand structures. With functions, loops, and conditionals, developers can produce clear code that is easy to maintain.

  6. Procedural Language − C follows a procedural paradigm that is often simpler and more straightforward for some types of programming tasks.

  7. Versatility − C language is a versatile programming language and it can be used for various types of software such as system applications, compilers, firmware, application software, etc.

Drawbacks of C Language

以下是C语言的缺点/缺陷−

The following are the disadvantages/drawbacks of C language −

  1. Manual Memory Management − C languages need manual memory management, where a developer has to take care of allocating and deallocating memory explicitly.

  2. No Object−Oriented Feature − Nowadays, most of the programming languages support the OOPs features. But C language does not support it.

  3. No Garbage Collection − C language does not support the concept of Garbage collection. A developer needs to allocate and deallocate memory manually and this can be error-prone and lead to memory leaks or inefficient memory usage.

  4. No Exception Handling − C language does not provide any library for handling exceptions. A developer needs to write code to handle all types of expectations.

Applications of C Language

以下是 C 语言的应用 −

The following are the applications of C language −

  1. System Programming − C language is used to develop system software which are close to hardware such as operating systems, firmware, language translators, etc.

  2. Embedded Systems − C language is used in embedded system programming for a wide range of devices such as microcontrollers, industrial controllers, etc.

  3. Compiler and Interpreters − C language is very common to develop language compilers and interpreters.

  4. Database Systems − Since C language is efficient and fast for low-level memory manipulation. It is used for developing DBMS and RDBMS engines.

  5. Networking Software − C language is used to develop networking software such as protocols, routers, and network utilities.

  6. Game Development − C language is widely used for developing games, gaming applications, and game engines.

  7. Scientific and Mathematical Applications − C language is efficient in developing applications where scientific computing is required. Applications such as simulations, numerical analysis, and other scientific computations are usually developed in C language.

  8. Text Editor and IDEs − C language is used for developing text editors and integrated development environments such as Vim and Emacs.

Getting Started with C Programming

要有效地学习 C，我们首先需要了解其结构。每个编程语言都有自己的编程结构。C 程序的典型结构包括几个部分。以下步骤展示了常规 C 程序的 C 结构 −

To learn C effectively, we need to understand its structure first. Every programming language has its programming structure. A typical structure of a C program includes several parts. The following steps show the C structure of a regular C program−

Include Header Files

包含必要的文件头，其中包含函数声明、 constants 和宏，可在一个或多个源代码文件中使用。一些流行的文件头如下 −

Include necessary header files that contain declarations of functions, constants, and macros that can be used in one or more source code files. Some popular header files are as −

stdio.h − 提供类似 printf 和 scanf 的输入和输出函数。

stdio.h − Provides input and output functions like printf and scanf.

#include <stdio.h>

stdlib.h − 包含涉及内存分配、rand 函数和其他实用函数的函数。

stdlib.h − Contains functions involving memory allocation, rand function, and other utility functions.

#include <stdlib.h>

math.h − 包含数学函数，如 sqrt 、 sin 、 cos 等。

math.h − Includes mathematical functions like sqrt, sin, cos, etc.

#include <math.h>

string.h − 包含用于操作字符串的函数，如 strcpy 、 strlen 等。

string.h − Includes functions for manipulating strings, such as strcpy, strlen, etc.

#include <string.h>

ctype.h − 用于测试和映射字符的函数，如 isalpha 、 isdigit 等。

ctype.h − Functions for testing and mapping characters, like isalpha, isdigit, etc.

#include <ctype.h>

stdbool.h − 定义布尔值数据类型和值 true 和 false 。

stdbool.h − Defines the boolean data type and values true and false.

#include <stdbool.h>

time.h − 包含用于处理日期和时间的函数。

time.h − Contains functions for working with date and time.

#include <time.h>

limits.h − 定义各种特定于实现的整数类型限制。

limits.h − Defines various implementation-specific limits on integer types.

#include <limits.h>

Macros and Constants

在整个程序中定义将要使用的宏或常量。宏和常量是可选项。

Define any macros or constants that will be used throughout the program. Macros and constants are optional.

#include <stdio.h>
#define PI 3.14159
int main() {
   float radius = 5.0;
   float area = PI * radius * radius;

   printf("Area of the circle: %f\n", area);
   return 0;
}
Area of the circle: 78.539749

Global Declarations in C

全局声明是可选的：

Global declarations are optional:

int globalVariable;
void sampleFunction();

声明全局 variables 和将在程序的不同部分使用的函数。参阅以下 example −

Declare global variables and functions that will be used across different parts of the program. Take a look at the following example −

#include <stdio.h>

// Global variable declaration
int globalVariable;

int main()
{
   // Rest of the program
   return 0;
}

Main Function

每个 C 程序都必须有一个 main function 。它是该程序的入口点。参阅以下 example −

Every C program must have a main function. It is the entry point of the program. Take a look at the following example −

int main() {
   float radius = 5.0;
   float area = PI * radius * radius;

   printf("Area of the circle: %f\n", area);
   return 0;
}

Functions in C

根据需要定义其他函数。main 函数可以调用这些函数。参阅以下 example ：

Define other functions as needed. The main function may call these functions. Take a look at the following example:

#include <stdio.h>

// Global function declaration
void samplefunction();

int main() {
   // Programming statements
   return 0;
}

// Global function definition
void samplefunction () {
   // Function programming statements implementation
}

C 程序的行数可以从 3 行到数百万行，并且应该写成一个或多个具有扩展名 ".c" 的文本文件；比如，hello.c。您可以使用 "vi" 、 "vim" 或任何其他文本编辑器将您的 C 程序写到文件中。

A C program can vary from 3 lines to millions of lines and it should be written into one or more text files with extension ".c"; for example, hello.c. You can use "vi", "vim" or any other text editor to write your C program into a file.

本教程假设您知道如何编辑文本文件以及如何在程序文件中编写源代码。

This tutorial assumes that you know how to edit a text file and how to write source code inside a program file.