Static v/s Dynamic memory:
- In C application, we can allocate the memory to store the information in 2 ways
- Static – fixed size
- Dynamic – size varies
Static memory:
- All primitive data types having fixed size of memory.
- Using primitive variables we can allocate fixed memory blocks to store the data.
- Derived data types are Array and String
- User defined data types are Structure and Union
- We can allocate the memory to derived types and user defined types in 2 ways.
Static allocation:
- Array can store more than 1 element but of same data type.
- String stores only characters as elements.
- Structure can store different types of data like Emp records, Student records, Account records and so on.
Dynamic memory:
- Once we allocate the memory, we can increase or decrease the size of memory block depends on requirement.
- We can allocate memory using pointers.
- Pointer can store a memory block address of any size.
When Static memory allocates?
- At Compile time (completely wrong)
- At runtime – while programming is running.
When Dynamic memory allocates?
- At runtime – while programming is running.
Who will allocate Static memory?
Every application run by OS.
OS allocate required memory to execute the application.
What is Compiler?
- It is a translator(program)
- It will check whether the program is syntactically correct or not.
- If the program follows syntax rules, it converts the source code into machine code.
Note that, compiler is not responsible for allocating the memory.
How can we allocate memory dynamically in C language?
- Using the functionality of stdlib.h header file.
- Stdlib.h header file is providing 4 standard methods to allocate and de-allocate the memory.
- Malloc()
- Calloc()
- Realloc()
- Free()
