The following example declares the variable x on line 1, which is different from the x it declares on line 2. The declared variable on line 2 has function prototype scope and is visible only up to the closing parenthesis of the prototype declaration. The variable x declared on line 1 resumes visibility after the end of the prototype declaration.
1 int x = 4; /* variable x defined with file scope */
2 long myfunc(int x, long y); /* variable x has function */
3 /* prototype scope */
4 int main(void)
5 {
6 /* . . . */
7 }The following program illustrates blocks, nesting, and scope. The example shows two kinds of scope: file and block. The main function prints the values 1, 2, 3, 0, 3, 2, 1 on separate lines. Each instance of i represents a different variable.
#include <stdio.h>
int i = 1; /* i defined at file scope */
int main(int argc, char * argv[])
*----- {
¹
¹ printf("%d\n", i); /* Prints 1 */
¹
¹ *--- {
¹ ² int i = 2, j = 3; /* i and j defined at block scope */
¹ ² /* global definition of i is hidden */
¹ ² printf("%d\n%d\n", i, j); /* Prints 2, 3 */
¹ ²
¹ ² *-- {
¹ ² ³ int i = 0; /* i is redefined in a nested block */
¹ ² ³ /* previous definitions of i are hidden */
¹ ² ³ printf("%d\n%d\n", i, j); /* Prints 0, 3 */
¹ ² *-- }
¹ ²
¹ ² printf("%d\n", i); /* Prints 2 */
¹ ²
¹ *--- }
¹
¹ printf("%d\n", i); /* Prints 1 */
¹
¹ return 0;
¹
*------ }