From 7e0f021a9aec35fd8e6725e87e3313b101d26f5e Mon Sep 17 00:00:00 2001 From: Tobias Klauser Date: Sun, 27 Jan 2008 11:37:44 +0100 Subject: Initial import (2.0.2-6) --- reference/C/SYNTAX/glo_int_vars.html | 214 +++++++++++++++++++++++++++++++++++ 1 file changed, 214 insertions(+) create mode 100644 reference/C/SYNTAX/glo_int_vars.html (limited to 'reference/C/SYNTAX/glo_int_vars.html') diff --git a/reference/C/SYNTAX/glo_int_vars.html b/reference/C/SYNTAX/glo_int_vars.html new file mode 100644 index 0000000..51991c4 --- /dev/null +++ b/reference/C/SYNTAX/glo_int_vars.html @@ -0,0 +1,214 @@ +Global and Local variables declaration. + + + + +

+ +

Global and Local variables.

+ +

Local variables

+Local variables must always be +defined +at the top of a block. +

+ +C++ has changed the rules regarding where you can define a +local variable. +Click here +for the low down. + +

+When a local variable is +defined +- it is not initalised by the system, you +must initalise it yourself.

+A local variable is +defined + inside a block and is only visable +from within the block. +

+ + + + +

+
+   main()
+   {
+       int i=4;
+       i++;
+   }
+
+

+ +

+When execution of the block starts the variable is +available, and when the block ends the variable 'dies'.

+A local variable is visible within nested blocks unless a variable with +the same name is +defined + within the nested block. +

+ + + + +

+
+   main()
+   {
+       int i=4;
+       int j=10;
+       
+       i++;
+      
+       if (j > 0)
+       {
+          printf("i is %d\n",i);      /* i defined in 'main' can be seen      */
+       }
+     
+       if (j > 0)
+       {
+          int i=100;                  /* 'i' is defined and so local to 
+                                       * this block */
+          printf("i is %d\n",i);      
+       }                              /* 'i' (value 100) dies here            */
+     
+       printf("i is %d\n",i);         /* 'i' (value 5) is now visable.        */
+   }
+
+

+ +

Global variables

+ + +C++ has enhanced the use of + global variables. + +

+Global variables ARE initalised by the system when you +define + them! +

+ + + + + + + +

Data Type	Initialser
int	0
char	'\0'
float	0
pointer	NULL

+ +

+In the next example i is a global variable, it can be seen and modified by + main and any other functions that may reference it. +

+ + + + +

+
+   int i=4;
+   
+   main()
+   {
+       i++;
+   }
+
+

+ +

+ +Now, this example has global and Internal variables. +

+ + + + +

+
+   int i=4;          /* Global definition   */
+   
+   main()
+   {
+       i++;          /* global variable     */
+       func
+   }
+
+   func()
+   {
+       int i=10;     /* Internal declaration */
+       i++;          /* Internal variable    */
+   }
+
+

+ +

+ +i in main is global and will be incremented to 5. i in +func is internal and will be incremented to 11. When control returns +to main the internal variable will die and and any reference to +i will +be to the global.

+ + +static variables can be 'seen' within all functions in this source file. At +link time, the static variables defined here will not be seen by the object +modules that are brought in.

Example:

+An Example program. +

Global and Local variables.

Local variables

Global variables

Example:

See Also: