Day#69 'C' Coding Challenge

What are the various storage classes in C and their differences?

Storage classes in C are:

• auto
• extern
• static
• register

auto:

• auto is the default storage class for variables. If no storage class is mentioned for a variable, then it is auto
• if the variable is not initialized, garbage shall be assigned
• can be accessed only within the block they are declared
• the life of the auto variable is till the end of the block in which it is declared

extern:

• used for global variables
• when extern is used before global variables, the variable can be used outside the file in which it is declared
• default value assigned is zero
• life of the extern is till the end of the particular program in which it is declared

static:

• A local variable has scope till the end of it's block/function. Once the block is exited, the local variable is more valid and it's value is lost. If there is a need for a particular local variable to hold it's value between function calls, then static need to be used
• default initial value is zero
• life of the static variable is till the end of the program

register:

• once declared with this type of keyword, then the variable is stored in registers
• major advantage is that registers have faster access
• register variable has the same property as auto variable, this meant
• default garbage value
• scope within a block
• life of variable only till end of block in which it is declared