C program to write c program without using main function
Download as PPTX, PDF1 like924 views
This document discusses three ways to write a C program without using the main function. The first way uses the #define preprocessor directive to replace "begin" with "main". The second way uses the ## token merging operator in a #define to merge the characters "m", "a", "i", and "n" together. The third way uses an argumented macro to define a function called "begin" that serves the same purpose as main.
![Run C Program Without Main Function
Conceptually C Program is meaningless without main Function . Every
Program Must have Main Function.
Main Function :
a] It is Entry Point of Every C Program.
b] All Predefined and User-defined Functions are called directly or
indirectly through the main.
c] So C Program Must have Main Function.
But I have decided not to write main and want to run C Program , How ?
We have 3 approaches of Writing C Program without using main().](https://image.slidesharecdn.com/cprogramtowritecprogramwithoutusing-170209173417/85/C-program-to-write-c-program-without-using-main-function-2-320.jpg)
C program to write c program without using main function
- 1. C Program to Write C Program Without using Main Function in 3 ways
- 2. Run C Program Without Main Function Conceptually C Program is meaningless without main Function . Every Program Must have Main Function. Main Function : a] It is Entry Point of Every C Program. b] All Predefined and User-defined Functions are called directly or indirectly through the main. c] So C Program Must have Main Function. But I have decided not to write main and want to run C Program , How ? We have 3 approaches of Writing C Program without using main().
- 3. 1 2 3 4 5 6 7 #include<stdio.h> #define begin main int begin() { printf("Hello"); return (0); } Way 1 : Using #define Preprocessor Directive
- 4. Way 1 : Using #define Preprocessor Directive What Preprocessor is doing Here ? • Save C Program using Extension .C • Before Program is given to compiler program is processed by Preprocessor . • begin main • Source Program is scanned from Left to Right and from Top to Bottom and “begin” is replaced by “main” • So Programmer feels that “He has written Code Without using Main , but internally begin is already converted into main”
- 5. 1 2 3 4 5 6 #include<stdio.h> #define begin m##a##i##n void begin() { printf("Hello"); } Way 2 : Using #define Token Merging Operator Explain ? • The ‘##‘ operator is called the token pasting or token merging operator. • That is we can merge two or more characters with it.
- 6. 1 2 3 4 5 6 #include<stdio.h> #define begin m##a##i##n void begin() { printf("Hello"); } Way 3 : Using Argumented Macro