4.1 Types of software and interrupts

Question 1

What is software?

Answer 1

a series of instructions written in a programming language that performs a function

Question 2

What are two types of system software?

Answer 2

operating system (OS) and utility programs

Question 3

What is Application software?

Answer 3

Application software provides the services that
the user requires

Question 4

What are 4 examples of generic names of application software?

Answer 4

Word Processor

Spreadsheet

Database

Web Browser

Question 5

Name all the roles of an Operating System

Answer 5

– managing files
– handling interrupts
– providing an interface
– managing peripherals and drivers
– managing memory
– managing multitasking
– providing a platform for running applications
– providing system security
– managing user account

Question 6

Describe how hardware, firmware and an operating system are required to run applications software.

Answer 6

The application software cannot run on a computer without an operating system. The operating system cannot run unless there instructions given to it, these are provided by the firmware. The firmware cannot run unless it is told to run, this is done using the bootstrap program, which is loaded when the computer first turns on and is run on the hardware.

Question 7

What is an interrupt?

Answer 7

a signal sent to a processor to tell it that its attention is needed

Question 8

What actions would cause interrupts to appear in the Hardware?

Answer 8

data input on a keyboard

error from hardware e.g. printer run out of paper

new hard drive device connected

Question 9

What actions would cause interrupts to appear in the software?

Answer 9

Division by 0

two processes attempting to access the same memory location

output required

Question 10

What is the interrupt handler?

Answer 10

a program that organizes interrupts into a order based on priorities

Question 11

What is the Interrupt service routine?

Answer 11

a program that receives an interrupt and performs a required action

Question 12

How is an interrupt handled using an interrupt service
routine?

Answer 12

• When the processor finishes its current fetch-decode-execute cycle (or before the starting the next FDE cycle), it checks the interrupt queue.
• It checks whether there is an interrupt with a higher priority than the current task it is processing.
• If it is, it:

                 Stores the current process and fetches the interrupt.
  
                 Checks the source of the interrupt.
  
                 Calls the relevant interrupt service routine (ISR). This is a sequence of 
                instructions that handle the interrupt.
  
                 When finished the stored process is returned to memory or another 
                higher-priority interrupt is fetched.

• If it isn’t, it runs another FDE cycle.