Fundamentals of Pointers in C
- 1. Fundamentals of pointers UNIT IV By : Shivanshu Verma
- 2. Introduction to Pointers A pointer is a variable that holds a memory address. This address is the location of another object(typically another variable) in a memory.
- 3. Pointers notations in C You can use a pointer on the right-hand side of an assignment statement to assign its value to another pointer. When both Pointers are the same type, the situation is straightforward.
- 4. Declaration of pointer A pointer is declared as “data-type*pointer-variable-name”. * symbol specifies it is a pointer variable. You must prefix * before variable name to declare it as a pointer. Pointer-variable-name is a valid C identifier i.e. the name of pointer variable.
- 5. Operations that can be performed on a computer Assignment Value finding Taking a pointer address Adding an integer to a pointer Incrementing a pointer Subtracting an integer from a pointer Decrementing a pointer Differencing comparision
- 6. Use of pointers in programming exercises Pointers are more efficient in handling arrays and structures Pointers are used to return multiple values from a function Pointer allow dynamic memory allocation and deallocation in C. Pointers allow to refer and pass a function as a parameter to functions
- 7. Parameters passing in pointers These are of two types Call by value Call by reference
- 8. Call by value In call by value method, the value of actual parameters is copied into the formal parameters in other words we can say that the value of variable is used in the function call in the call by value method. The actual parameters is the argument which is used in the function call whereas formal parameter is the argument which is used in the function definition.
- 9. Call by reference In call by reference, the address of the variable is passed into the function call as the actual parameters. The value of the actual parameters can be modified by changing the formal parameter since the address of the actual parameter is passed.
- 10. Array and character using pointers
- 11. Dynamic Allocation It can be done by four methods 1. Malloc 2. Calloc 3. Realloc 4. free
- 12. Malloc It stores data in a one memory chunk It does not initializes memory at 0 When memory is insufficient it points at NULL value Syntax: <pointer_name>=(cast type *)malloc(size)
- 13. Calloc It creates multiple block of memory It points at NULL value if memory is insufficient It initializes memory at 0 Suntax : <pointer_name>=(cast_type *)calloc(n,size)
- 14. Realloc It is used to increase or decrease the size of memory. Basically used after malloc or calloc Syntax: <pointer_name>=realloc(ptr_name,new size)
- 15. Free Put it at the place(usually end of program) to remove the memory of at pointer Syntax: free(pointer_name)
- 16. Thank You