variable definition and actual initialization using extern variable in c programming language

C Programming Language Variable in C Language (Article) Variable in C Language (Program)

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This C program demonstrates the use of external variable declarations and definitions. External variables a, b, c, and f are declared at the beginning of the program using the extern keyword, indicating they are defined elsewhere. In the main function, these variables are then defined and initialized: a and b are assigned values of 10 and 20, respectively, and c is calculated as their sum. The value of c is printed using printf. A floating-point division is performed, and the result is assigned to f, which is then printed. The program outputs the values of c and f before terminating.

Program:

<span class="com">#include</span><span class="str">"stdio.h"</span><span class="pln"> 
</span><span class="com">// Variable declaration:</span><span class="pln">
</span><span class="kwd">extern</span><span class="pln"> </span><span class="kwd">int</span><span class="pln"> a</span><span class="pun">,</span><span class="pln"> b</span><span class="pun">;</span><span class="pln">
</span><span class="kwd">extern</span><span class="pln"> </span><span class="kwd">int</span><span class="pln"> c</span><span class="pun">;</span><span class="pln">
</span><span class="kwd">extern</span><span class="pln"> </span><span class="kwd">float</span><span class="pln"> f</span><span class="pun">;</span><span class="pln">

</span><span class="kwd">int</span><span class="pln"> main </span><span class="pun">()</span><span class="pln"> </span><span class="pun">{</span><span class="pln">

   </span><span class="com">/* variable definition: */</span><span class="pln">
   </span><span class="kwd">int</span><span class="pln"> a</span><span class="pun">,</span><span class="pln"> b</span><span class="pun">;</span><span class="pln">
   </span><span class="kwd">int</span><span class="pln"> c</span><span class="pun">;</span><span class="pln">
   </span><span class="kwd">float</span><span class="pln"> f</span><span class="pun">;</span><span class="pln">
 
   </span><span class="com">/* actual initialization */</span><span class="pln">
   a </span><span class="pun">=</span><span class="pln"> </span><span class="lit">10</span><span class="pun">;</span><span class="pln">
   b </span><span class="pun">=</span><span class="pln"> </span><span class="lit">20</span><span class="pun">;</span><span class="pln">
  
   c </span><span class="pun">=</span><span class="pln"> a </span><span class="pun">+</span><span class="pln"> b</span><span class="pun">;</span><span class="pln">
   printf</span><span class="pun">(</span><span class="str">"value of c : %d \n"</span><span class="pun">,</span><span class="pln"> c</span><span class="pun">);</span><span class="pln">

   f </span><span class="pun">=</span><span class="pln"> </span><span class="lit">70.0</span><span class="pun">/</span><span class="lit">3.0</span><span class="pun">;</span><span class="pln">
   printf</span><span class="pun">(</span><span class="str">"value of f : %f \n"</span><span class="pun">,</span><span class="pln"> f</span><span class="pun">);</span><span class="pln">
 
   </span><span class="kwd">return</span><span class="pln"> </span><span class="lit">0</span><span class="pun">;</span><span class="pln">
</span><span class="pun">}</span>

Output:

value of c : 30
value of f : 23.333334
Press any key to continue . . .

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