0Every variable has a memory location and every memory location has its address defined which can be accessed using ampersand (&) operator, which denotes an address in memory. Consider the following example, which prints the address of the variables defined:
int main () { int var1; char var2[10]; printf("Address of var1 variable: %x\n", &var1 ); printf("Address of var2 variable: %x\n", &var2 ); return 0;}
Output: Address of var1 variable: bff5a400Address of var2 variable: bff5a3f6
A pointer is a variable whose value is the address of another variable, i.e, direct address of the memory location. Like any variable or constant, you must declare a pointer before using it to store any variable address. The general form of a pointer variable declaration is:
type *var-name;
Here, type is the pointer's base type, it must be a valid C data type and var-name is the name of the pointer variable. The asterisk * used to declare a pointer is the same asterisk used for multiplication. However, in this statement the asterisk is being used to designate a variable as a pointer. Take a look at some of the valid pointer declarations:
int *ip; /* pointer to an integer */double *dp; /* pointer to a double */float *fp; /* pointer to a float */char *ch /* pointer to a character */
#include int main () { int var = 20; /* actual variable declaration */ int *ip; /* pointer variable declaration */ ip = &var; /* store address of var in pointer variable*/ printf("Address of var variable: %x\n", &var ); /* address stored in pointer variable */ printf("Address stored in ip variable: %x\n", ip ); /* access the value using the pointer */ printf("Value of *ip variable: %d\n", *ip ); return 0;}
Output: Address of var variable:bffd8b3cAddress stored in ip variable:bffd8b3cValue of *ip variable:20
