Case (i): Modifier ‘auto’ or no modifier

• It means that there is a ROM allocation for the variable, if it is initialized in the program.
• RAM is allocated for the variable if it is not initialized in the program.

Case (ii): Modifier ‘unsigned’

• Modifier for short/ int/ long data types
• Directive to permit only positive values

Case (iii): Modifier ‘static’

• Declaration is inside a function block
• Directive to compiler that the variable should be accessible outside the function block also.
• Helps when several tasks are executed in co-operation.

Case (iv): Modifier ‘static’

• Declaration is outside a function block
• Not usable outside the class or module in which it is declared.
• ROM allocated by locator for function codes.

Case (v): Modifier ‘const’

• Declaration is outside a function block
• Must be initialized by program
• ROM allocation by locator

Case (vi): Modifier ‘register’

• Declaration is inside a function block
• Must be initialized by a program
• A CPU register is temporarily allocated when needed
• No ROM/ RAM allocation

Case (vii): Modifier ‘interrupt’

• On the entry of function code the compiler is directed to save all processors’ registers
• On return from function compiler is directed to restore them

Case (viii): Modifier ‘extern’

• Directs compiler to look for data type declaration or a function in a module other than the current one.

Case (ix): Modifier ‘volatile’

• Declaration is outside a function block
• Warning to compiler that an event can change its value or its change represents an event.

Case (x): Modifier ‘volatile static’

• Declaration is inside a function block
• Static - directive to compiler that variable should be accessible outside function block
• Volatile - compiler cannot optimize the code
• No ROM/ RAM allocation by locator