C/Language Basics/Variable Scope

A free-standing block statement

<source lang="cpp">

1. include <stdio.h>

int main(void) {

 int i;
 {  
    i = 1;
    printf("%d", i);
 }
 return 0;

}

      </source>

Assign value to global variable

<source lang="cpp">

1. include <stdio.h>

int count; int main(void) {

 extern int count; /* this refers to global count */
 count = 10;
 printf("%d", count);
 return 0;

}

      </source>

Define and use global variable and function

<source lang="cpp">

1. include <stdio.h>

int i =0; //Global variable void f1(void) {

   int k; // local variable for f1.
   i = 50;

}

main() {

    int j;  // local variable in main
    
    f1();    
    
    i =0;
    
    printf(" i in main %d\n",i);
    f1();
    
    printf(" i after call%d\n",i);

}

      </source>

Define and use Global variables

<source lang="cpp">

1. include <stdio.h>

int count = 0; /* Declare a global variable */ /* Function prototypes */ void test1(void); void test2(void); void main() {

  int count = 0;             /* This hides the global count */
  for( ; count < 5; count++)
  {
    test1();
    test2();
  }

} /* Function test1 using the global variable */ void test1(void) {

  printf("\ntest1   count = %d ", ++count);

} /* Function test2 using a static variable variable */ void test2(void) {

  static int count;          /* This hides the global count */
  printf("\ntest2   count = %d ", ++count);

}

      </source>

Define block inside a function

<source lang="cpp">

1. include <stdio.h>

main() {

   int  i = 10; 
   
   { 
       int i = 0;
       for( i=0;i<2;i++) {
           printf("i = %d\n",i);
      }
   }  
   printf("i = %d\n",i);

}

      </source>

Define local variable for a function

<source lang="cpp"> int i =0; //Global variable void f(void); main() {

   int i ;      // local variable for main 
   i =0; 
   
   printf("value of i in main %d\n",i); 
   
   f(); 
   
   printf("value of i after call%d\n",i); 

} void f(void) {

   int i=0; //local variable for f
   i = 50;

}

      </source>

Define variable in a block

<source lang="cpp">

1. include <stdio.h>

main() {

   int  k = 10;
   int i = 100;
   {
       int i;
       for(i = 0; i < 2; i++ ) {
           printf("i = %d\n",i);
       }
   }
   printf("i = %d\n",i);

}

      </source>

Global variable and function

<source lang="cpp">

1. include <stdio.h>

int count; /* count is global */ void func1(void); void func2(void); int main(void) {

 count = 100;
 func1();
 return 0;

} void func1(void) {

 int temp;
 temp = count;
 func2();
 printf("count is %d", count); /* will print 100 */

} void func2(void) {

 int count;
 for(count=1; count<10; count++)
   putchar(".");

}

      </source>

Our own power function with parameters

<source lang="cpp">

1. include <stdio.h>

int power(int m, int e); int main(void) {

 int m, e;
 m = 3;
 e = 4;
 printf("%d to the %d is %d\n", m, e, power(m, e));
 printf("5 to the 6th is %d\n", power(5, 6));
 printf("4 to the 4rd is %d\n", power(4, 4));
 return 0;

} /* Parameterized version of power. */ int power(int m, int e) {

 int temp;
 temp = 1;
 for( ; e > 0; e--) 
     temp = temp * m;
 return temp;

}

      </source>

Use global variable in function

<source lang="cpp">

1. include <stdio.h>

int max; /* a global variable */ void f(void) {

 int i;
 for(i=0; i<max; i++) 
     printf("%d ", i);

}

int main(void) {

 max = 10;
 f();
 return 0;

}

      </source>

use global vars

<source lang="cpp">

1. include <stdio.h>

/* global definition of first and last */ int first = 10, last = 20; int main(void) {

 extern int first, last; 
 printf("%d %d", first, last);
 return 0;

}

      </source>

Variable scope: in and out a block

<source lang="cpp">

1. include <stdio.h>

void main() {

  int c = 0;   /* Declared in outer block */
  do
  {
    int c = 0; /* This is another variable called c */
    ++c ;       /* this applies to inner c   */
    printf("\n c  = %d ", c );  
  }
  while( ++c  <= 3 );     /* This works with outer c */
  /* Inner c  is dead, this is outer */
  printf("\n c = %d\n", c ); 

}

      </source>

Variable scope:inside a function

<source lang="cpp">

1. include <stdio.h>

int main(void) {

 int x;
 x = 10;
 if(x == 10) {
   int x; /* this x hides the outer x */
   x = 99;
   printf("Inner x: %d\n", x);
 }
 printf("Outer x: %d\n", x);
 return 0;

}

      </source>

Work with global variable

<source lang="cpp">

1. include <stdio.h>

int sample; int main(void) {

 printf("%p", &sample);
 return 0;

}

      </source>