To demonstrate a practical example of dynamic memory, we created a program that can make a list of any length.
Regular arrays in C have a fixed length and cannot be changed, but with dynamic memory we can create a list as long as we like : Continue reading C Memory Management Example
When you no longer need a block of memory you should deallocate it. Deallocation is also referred to as “freeing” the memory.
Dynamic memory stays reserved until it is deallocated or until the program ends.
Once the memory is deallocated it can be used by other programs or it may even be allocated to another part of your program.
If the amount of memory you reserved is not enough, you can reallocate it to make it larger.
Reallocating reserves a different (usually larger) amount of memory while keeping the data that was stored in it.
You can change the size of allocated memory with the realloc() function.
The realloc() function takes two parameters:
int *ptr2 = realloc(ptr1, size);
Dynamic memory behaves like an array, with its data type specified by the type of the pointer.
As with arrays, to access an element in dynamic memory, refer to its index number:
ptr[0] = 12;
You can also dereference the pointer to access the first element:
*ptr = 12;
The process of reserving memory is called allocation. The way to allocate memory depends on the type of memory.
C has two types of memory: Static memory and dynamic memory.
Static memory is memory that is reserved for variables before the program runs. Allocation of static memory is also known as compile time memory allocation.
C automatically allocates memory for every variable when the program is compiled. Continue reading C Allocate Memory
Memory management is the process of handling how much memory a program uses through different operations.
Understanding how memory works in C is important. When you create a basic variable, C will automatically reserve space for that variable. An int variable for example, will typically occupy 4 bytes of memory, while a double variable will occupy 8 bytes of memory. Continue reading C Memory Management
An enum is a special type that represents a group of constants (unchangeable values).
To create an enum, use the enum keyword, followed by the name of the enum, and separate the enum items with a comma:
enum Level {
LOW,
MEDIUM,
HIGH
};
Note that the last item does not need a comma.
It is not required to use uppercase, but often considered as good practice.
Enum is short for “enumerations”, which means “specifically listed”.
Structures (also called structs) are a way to group several related variables into one place. Each variable in the structure is known as a member of the structure.
Unlike an array, a structure can contain many different data types (int, float, char, etc.).
In the previous chapter, we wrote to a file using w and a modes inside the fopen() function.
To read from a file, you can use the r mode:
FILE *fptr;
// Open a file in read mode
fptr = fopen("filename.txt", "r");
This will make the filename.txt opened for reading.
It requires a little bit of work to read a file in C. Hang in there! We will guide you step-by-step.
Next, we need to create a string that should be big enough to store the content of the file. Continue reading C Read Files
Let’s use the w mode from the previous chapter again, and write something to the file we just created.
The w mode means that the file is opened for writing. To insert content to it, you can use the fprintf() function and add the pointer variable (fptr in our example) and some text: Continue reading C Write To Files