12 1. const pointer, typedef
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This document discusses const and pointers in C/C++. It explains that: 1) A const pointer can point to const variables but not non-const, and a non-const pointer cannot point to const variables. 2) A const pointer variable's value cannot be changed after initialization, but it can point to non-const variables. 3) typedef allows defining new types with shorter names for readability, such as defining unsigned short as ushort.
12 1. const pointer, typedef
- 2. 2 const and Pointer const int * – p is a pointer variable that can hold an address of const integers – Cannot assign value 9 to the variable pointed by p, because the variable which p points to is const int const int a = 7; const int *p = &a; // possible a = 8 ; // impossible *p = 9 ; // impossible
- 3. 3 const and Pointer const int * – p, which is declared to point to const integers, can also hold an address of integer type – a can not be modified through by p, because p is declared as const int * • Any variable which is accessed through p is considered as const int int a = 7; const int *p = &a; // possible a = 8 ; // possible *p = 9 ; // impossible
- 4. 4 const and Pointer int * and const int – p, which is declared to point to normal integers, cannot hold the address of const integers – if it is possible, we can change the const variable through p • Eg) *p = 8 const int a = 7; int *p = &a; // impossible
- 5. 5 const and Pointer int * const – p is a const pointer variable which can point to normal integers – You cannot change its value because it is a const variable – p is a const pointer variable of normal integer, so p cannot hold the address of const integers int a = 7, b = 8 ; int * const p = &a; // possible p = &b; // impossible const int a = 7; int * const p = &a; // impossible
- 6. 6 const and Pointer const int * const – p is a const pointer variable of const integers, so p can be initialized once but cannot be changed anymore const int a = 7, b = 8 ; const int * const p = &a; // possible p = &b; // impossible *p = 6; // impossible int a = 7, b = 8 ; const int * const p = &a; // possible p = &a; // impossible *p = 6; // impossible
- 7. typedef Example – Type name is too long – Can we make it shorter? 7 unsigned short var1 ; unsigned short var2 ; … ushort var1 ; ushort var2 ; …
- 8. typedef typedef – old name can be consist of many words – But, new name should be consist of one word. 8 typedef old name new name typedef unsigned short ushort ; void main() { ushort var1 ; ushort var2 ; … }
- 9. typedef Example 9 typedef int Int ; typedef Int INT ; typedef unsigned long ulong ; void main() { ulong var1 ; Int k ; INT m ; … }