AISWARYA. T.V.

ROLLNO :54 S4 BIOMEDICAL

STACK

MACROS

PROCEDURES

CONTENTSINTERRUPT SERVICE ROUTINES

STACKS

STACK is a LAST- INPUT -FIRST -OUTPUT read/write memory

STACKS is a block of memory that may be used for temporarily storing the contents of the registers inside the CPU. The stack is a block of memory locations which is accessed using the STACK POINTER and STACK SEGMENT registers.

In other words ,it is a a top-bottom data structure whose elements are accessed using the SP and SS registers.

As we go on storing storing the data words into the stack, the pointer goes on decrementing and on other hand, pointer goes on incrementing as we go on retriving the data.

The data in the stack register again may be transferred to stack register whenever is required by the CPU.

PUSH : The process of storing the data in the stack is called ’pushing into’ the stack .

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PULL :The process of transferring of data from stack to the CPU is called ‘POPPING OFF’

INTERRUPT &INTERRUPT SERVICE ROUTINES

INTERRUPT SERVICE ROUTINES

MEANING OF INTERRUPT IS TO MAKE A BREAK IN THE SEQUENCE OF OPERATIONS.

Interrupt Service Routinees (ISR) are the programs to be executed by interrupting the main program execution of CPU ,after an interrupt request appears.

After executing ISR, the control is transferred back again to the main program which was being executed at the time of interruption .

Definition of the macro

A macro is a group of repetitive instructions in a program which are codified only once and can be used as many times as necessary. The main difference between a macro and a procedure is that in the macro the passage of parameters is possible and in the procedure it is not, this is only applicable for the TASM - there are other programming languages which do allow it. At the moment the macro is executed each parameter is substituted by the name or value specified at the time of the call.

We can say then that a procedure is an extension of a determined program,while the macro is a module with specific functions which can be used bydifferent programs.Another difference between a macro and a procedure is the way of calling each one, to call a procedure the use of a directive is required, on the other hand the call of macros is done as if it were an assembler instruction.

MACROS

.avoid repetitious SAS code

.create generalisable and flexible SAS code

.pass information from one part of a SAS job to another

.conditionally execute data steps and PROCs

.dynamically create code at execution time