Introduction to C language

C language is a universal, process-oriented computer programming language.

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

In 1978, Blaine Collingham (Brian Kernighan) and Dennis Ritchie (Dennis Ritchie) made the first publicly available description of C, now known as the K&r standard.

Unix operating systems, C compilers, and almost all UNIX applications are written in C. for various reasons, C language has now become a widely used professional language.

C is a widely used computer language that is as popular as the Java programming language, and is widely used by modern software programmers.

The current up-to-date C language standard for C11, before it the C language standard for C99.

The C language test is usually used in computer grade exams.

Eg: "Hello world"

1 #include <stdio.h>2  3int  main ()4{5      /**     /6 printf ("Hello, world! \ n"); 7  8     return 0 ; 9 }

Instance parsing:

• All C language programs need to include the main () function. The code executes from the main () function.
• / * * * for Multiline comment description,//For single line comment.
• printf () is used to format the output to the screen. The printf () function is declared in the "stdio.h" header file.
• stdio.h is a header file (standard input Output header file), #include is a preprocessing command used to introduce a header file. When the compiler encounters the printf () function, a compilation error occurs if the stdio.h header file is not found.
• return 0; Statement is used to indicate exiting a program.

The advantages of the C language:

• Easy to learn.
• Structured language.
• It produces high-efficiency programs.
• It can handle the underlying activity.
• It can be compiled on a variety of computer platforms.

About C

• The C language was invented to write UNIX operating systems.
• The C language is based on the B language, and B is probably introduced in 1970.
• The C language standard was established in 1988 by the American National Standards Association (ANSI, full name American Nation standard Institute).
• As of 1973, the UNIX operating system was fully written in C language.
• At present, C language is the most widely used system programming language.
• Most of the advanced software is implemented using the C language.
• Today's most popular Linux operating systems and RDBMS (relational database Management system: relational databases Management systems) MySQL are written in C language.

Why use C?

The C language was originally used for system development work, especially the program that composed the operating system. Since the code produced by C is running at the same speed as the code written in assembly language, C language is used as the system development language. Here are a few examples of using C:

• Operating system
• Language compilers
• Assembler Series
• Text Editor
• Printer
• Network Drive
• Modern programs
• Database
• Language interpreter
• Entity Tools

C Program

A C language program, which can be 3 rows or millions of lines, which can be written in one or more text files with the extension ". C" , for example,hello.c. You can use "VI","vim" or any other text editor to write your C language program.

C11

C11 (also known as C1X) means ISO standard ISO/IEC 9,899:2011 and is currently the latest C language standard. The C language standard before it is C99.

New features

• Alignment (Alignment) normalization (including _alignas, alignof operators, Aligned_alloc functions, and <stdalign.h> header files). The

• _noreturn function tag, similar to GCC's __attribute__ ((Noreturn)). The

• _generic keyword.

• Multithreading (multithreading) support, including:
  _thread_local storage type identifier,<threads.h> header file, which contains the thread creation and management functions. The
  _atomic type modifier and the <stdatomic.h> header file. Support for enhanced Unicode for

• . Enhanced support for Unicode, based on the C Unicode Technology report, ISO/IEC TR 19,769:2004. Includes the addition of char16_t and char32_t data types for utf-16/utf-32 encoding, and a header file <uchar.h> that contains a Unicode string conversion function.

• Removes the gets () function and replaces it with a new, more secure function, gets_s (). The

• Adds a boundary check function interface that defines new security functions such as fopen_s (), strcat_s (), and so on.

• Adds more floating-point processing macros (macros).

• Anonymous struct/consortium support. This has already existed in GCC and C11 it into the standard. The

• Static assertion (static assertions), _static_assert (), is processed after the interpretation #if and #error.

• New fopen () mode, ("... x"). o_creat| similar to POSIX O_EXCL, which is more commonly used in file locks.

• Adds the Quick_exit () function as the third way to terminate the program. When exit () fails, you can do the least cleanup work.

Introduction to C language