C Programming: Arrays

Array Initialization

• An array must be initialized when declared, or the compiler will show an error "size of array is unknown or zero".
• There are four ways to initialize one-dimensional arrays in C programming:
  • Initialize at the time of declaration, e.g., int a[] = {10, 20, 30, 40, 50};.
  • Initialize all elements with 0 (zero).
  • Initialize elements individually, e.g., int a; a = 10; a = 20; ....
  • Define the size of an array by initializing its elements.

Return Statement

• The return statement terminates the execution of a function and returns control to the calling function.
• It can also return a value to the calling function.
• The point of functions is to take in inputs and return something.

Array Definition

• An array is a collection of elements of the same type placed in contiguous memory locations.
• Array elements can be individually referenced by using an index to a unique identifier.

Storage Classes in C

Auto Storage Class

• The auto storage class is used for local variables.
• Variables defined using auto are called local variables.
• The scope of an auto variable is limited to the particular block only.
• Auto variables contain a garbage value by default.

Extern Storage Class

• The extern storage class is used for global variables and functions shared between two or more files.
• Extern variables are accessible throughout the program.
• Extern variables cannot be initialized, as they have already been defined in the original file.

Static Storage Class

• Static variables are used within functions/files as local static variables or as global variables.
• Static local variables retain their value between function calls or block and remain visible only to the function or block in which they are defined.
• Static global variables are global variables visible only to the file in which they are declared.
• Static variables have a default initial value of zero and are initialized only once in their lifetime.

Register Storage Class

• The register storage class is used to store local variables within functions or blocks in CPU registers instead of RAM for quick access.