Is it fine to jot down “void main()” or “main()” in C/C++?

and

Prerequisite : Fork system call, Wait call
A signal could be a software package generated interrupt that's sent to a process by the OS attributable to once user press ctrl-c or another method tell one thing to the present method.
There area unit fix set of signals which will be sent to a method. signal area unit known by integers.
Signal variety have symbolic names. as an example SIGCHLD is variety of the signal sent to the parent method once kid terminates.
Examples:

0

0

0

0

……

0

0

0

0

Blocked Signals :

    31         30      29         28      ......       3           2          1           0

0

0

0

0

……

0

0

0

0

// CPP program to illustrate 
// default Signal Handler 
#include<stdio.h> 
#include<signal.h> 

int main() 
{ 
signal(SIGINT, handle_sigint); 
while (1) 
{ 
printf(“hello world\n”); 
sleep(1); 
} 
return 0; 
} 


Output: Print hello world infinite times. If user presses ctrl-c to terminate the process because of SIGINT signal sent and its default handler to terminate the process.









When a symbol handler executes, the parameter passed to that is that the range of the signal. A applied scientist will use identical signal handler operate to handle many signals. during this case the handler would wish to ascertain the parameter to examine that signal was sent. On the opposite hand, if a symbol handler function solely handles one signal, it isn’t necessary to hassle examining the parameter since it'll continuously be that signal number.

// CPP program to illustrate 
// User-defined Signal Handler 
#include<stdio.h> 
#include<signal.h> 

// Handler for SIGINT, caused by 
// Ctrl-C at keyboard 
void handle_sigint(int sig) 
{ 
printf("Caught signal %d\n", sig); 
} 

int main() 
{ 
signal(SIGINT, handle_sigint); 
while (1) ; 
return 0; 
} 

In most programing languages, a jiffy loop may be a control flow statement that enables code to be executed repeatedly supported a given mathematician condition. The mathematician condition is either true or false

#include<stdio.h> 
int main() 
{ 
int i = 1; 
printf("%d %d %d\n", i++, i++, i); 
return 0; 
} 


So the return type void doesn’t follow the quality and it’s one thing allowed by bound compilers.Let us mention second example. Note the subsequent statement in C standard is listed below unspecified behavior.

OVERVIEW OF C

C could be a general, problem-oriented language that was originally developed by Dennis M. Ritchie to develop the UNIX systemsoftware package at Bell Labs. C was originally 1st enforced on the DEC PDP-11 pc in 1972.
In 1978, Brian Kernighan and Dennis Ritchie made the primary publically out there description of C, currently called the K&R commonplace.
The UNIX system software package, the C compiler, and primarily all UNIX system application programs are written in C. C has currently become a wide used skilled language for varied reasons:
• Easy to be told
• Structured language
• It produces economical programs
• It will handle low-level activities
• It may be compiled on a spread of pc platforms



Facts regarding C

• C was fancied to write down Associate in Nursing software package referred to as UNIX system.
• C could be a successor of B language that was introduced round the early Seventies.
• The language was formalized in 1988 by the yank National commonplace Institute (ANSI).
• The UNIX system OS was altogether written in C.
• Today C is that the most generally used and well-liked System artificial language.
• Most of the progressive code are enforced mistreatment C.
• Today's hottest UNIX system OS and RDBMS MySQL are written in C.


Why Use C?

C was at first used for system development work, notably the programs that make-up the software package. C was adopted as a system development language as a result of it produces code that runs nearly as quick because the code written in programing language. Some samples of the employment of C would possibly be:
• Operating Systems
• Language Compilers
• Assemblers
• Text Editors
• Print Spoolers
• Network Drivers
• Modern Programs
• Databases
• Language Interpreters
• Utilities

C Programs
A programme will vary from three lines to ample lines and it ought to be written into one or a lot of text files with extension ".c"; for instance, hello.c. you'll use "vi", "vim" or the other text editor to write down your programme into a file.
This tutorial assumes that you just acumen to edit a document and the way to write down ASCII text file within a program file

C Language Introduction

C may be a procedural artificial language. it absolutely was at the start developed by Dennis Ritchie between 1969 and 1973. it absolutely was in the main developed as a system artificial language to jot down OS. the most options of C language embody low-level access to memory, straightforward set of keywords, and clean vogue, these options create C language appropriate for system programming like OS or compiler development.
Many later languages have borrowed syntax/features directly or indirectly from C language. Like syntax of Java, PHP, JavaScript and lots of alternative languages is principally supported C language. C++ is sort of a superset of C language (There area unit few programs that will compile in C, however not in C++).

Beginning with C programming:

Structure of a C program
After the on top of discussion, we are able to formally assess the structure of a C program. By structure, it's meant that any program will be written during this structure solely. Writing a C program in the other structure can therefore result in a Compilation Error.



Header Files Inclusion: the primary and foremost element is that the inclusion of the Header files in an exceedingly C program.
A header file may be a file with extension .h that contains C operate declarations and macro definitions to be shared between many supply files.



Some of C Header files

stddef.h – Defines several useful types and macros.
stdint.h – Defines exact width integer types.
stdio.h – Defines core input and output functions
stdlib.h – Defines numeric conversion functions, pseudo-random network generator, memory allocation
string.h – Defines string handling functions
math.h – Defines common mathematical functions
Syntax to include a header file in C:

#include <(header_file_name).h>
Main Method Declaration: The next part of a C program is to declare the main() function. The syntax to declare the main function is:
Syntax to Declare main method:

int main()
{}

Variable Declaration: subsequent a part of any program is that the variable declaration. It refers to the variables that area unit to be utilized in the operate. Please note that in program, no variable may be used while not being declared. conjointly in an exceedingly program, the variables area unit to be declared before any operation within the operate.
Example:

int main()
{
    int a;
.
.

Body: Body of a operate in program, refers to the operations that area unit performed within the functions. It is something like manipulations, searching, sorting, printing, etc.
Example:


int main()
{
    int a;

    printf("%d", a);
.
.

Return Statement: The last half in any programme is that the come statement. The come statement refers to the returning of the values from a operate. This come statement and come worth depend on the return-type of the operate. as an example, if the come kind is void, then there'll be no come statement. In the other case, there'll be a come statement and therefore the come worth are of the sort of the required return-type.
Example:

int main()
{
    int a;

    printf("%d", a);

    return 0;
}



#include <stdio.h>
int main(void)
{
printf("GeeksQuiz");
return 0;
}

Let us analyze the command by line.
Line 1: [ #include ] during a C program, all lines that begin with # square measure processed by preprocessor that may be a program invoked by the compiler. during a} very basic term, preprocessor takes a C program and produces another C program. The created program has no lines beginning with #, all such lines square measure processed by the preprocessor. within the on top of example, preprocessor copies the preprocessed code of stdio.h to our file. The .h files square measure referred to as header files in C. These header files typically contain declaration of functions. we'd like stdio.h for the operate printf() employed in the program.





Line two [ int main(void) ] There should to be start line from wherever execution of compiled C program begins. In C, the execution usually begins with initial line of main(). The void written in brackets indicates that the most doesn’t take any parameter (See this for additional details). main() are often written to require parameters conjointly. we'll be covering that in future posts.
The int written before main indicates come back style of main(). the worth came by main indicates standing of program termination. See this post for additional details on come back sort.

Line three and 6: [ ] In C language, a try of frizzy brackets outline a scope and primarily employed in functions and management statements like if, else, loops. All functions should begin and finish with frizzy brackets.

Line four [ printf(“Sayed”); ] printf() may be a commonplace library operate to print one thing on commonplace output. The punctuation mark at the top of printf indicates line termination. In C, punctuation mark is often wont to indicate finish of statement.

Line five [ come back 0; ] The come back statement returns the worth from main(). The came worth could also be utilized by package to grasp termination standing of your program. the worth zero usually suggests that no-hit termination.

Linux: For UNIX operating system, gcc comes bundled with the UNIX operating system, Code Blocks may also be used with UNIX operating system.

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