C-Definition

Software-Engineering

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# What is C?

C is a general-purpose programming language created by Dennis Ritchie at the Bell Laboratories in 1972.

It is a very popular language, despite being old. The main reason for its popularity is because it is a fundamental language in the field of computer science.

C is strongly associated with UNIX, as it was developed to write the UNIX operating system.

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# Why Learn C?

• one of the most popular programming language in the world
• similar syntax to other programming languages (Java, Python, C++, C#, …)
• C is very fast, compared to other programming languages, like Java and Python
• C is very versatile; it can be used in both applications and technologies

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# Difference C vs C++

• C++ was developed as an extension of C - both have similar syntax
• The main difference: C++ support classes and objects, while C doesn’t

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# simple C programm

#include <stdio.h>
int main int argc , char ** argv
{
	// print a message in the terminal
	printf ("Main Program Entry point \n");
	// returns an integer 
	return 0;
}
 
// Main function without parameters
int main(void) { ... }

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# Include libraries

with the #include ... syntax

• <> .. include standard system libraries
  • <stdio.h>
• "" .. include local library from path
  • ”myLib.h”

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# Header files

you can create own librariese or split functionality

Usage:

• global defines (not for global variables!)
• reusable software

myLib.h:

#ifndef __MYLIB_   // Check if the macro __MYLIB_ is not defined
#define __MYLIB_   // Define the macro __MYLIB_
 
/* Function prototype for a global function */
int mylibfnc(int param);
 
#endif              // End of the conditional compilation block

myLib.c:

#include <stdio.h>
// include Header file
#include "myLib.h"
 
// global function
int mylibfnc(int param)
{
	printf("Doing some library stuff... param= %d \n", param);
	return 0;
}

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# Global Variables

• allowed
• not nice!
• memory reserved at runtime
• do not use Header files for global vars
• define global vars only once!

Access from all files

#include <stdio.h>
int globVar1 = 3;      // global variable
extern int globVar2;   // var is defined somewhere else
#include "myLib.h"
 
// global function
int mylibfnc(int param)
{
	printf("Doing some library stuff... param=%d \n", param);
	return 0;
}

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