Lesson 4 : Interrupts

4.1 Types of software and interrupts
4.1.3 Running of applications
Watch the video for Interrupts
https://www.youtube.com/watch?v=DYaXpfyp2II

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4.1 Types of software and interrupts
4.1.3 Running of applications
Interrupts

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An interrupt is a signal sent from a device or from software to the microprocessor. This will cause the microprocessor to
temporarily stop what it is doing so that it can service the interrupt. Interrupts can be caused by:
» a timing signal
» an input/output process (for example, a disk drive or printer requiring more data)
» a hardware fault (for example, a paper jam in the printer)
» user interaction (for example, the user presses a key (or keys) on a keyboard, such as <CTRL><ALT><BREAK>, which
causes the system to be interrupted)
» software errors that cause a problem (for example, an .exe file that cannot be found to initiate the execution of a
program, two processes trying to access the same memory location, or an attempt to divide by zero).
-Once the interrupt signal is received, the microprocessor either carries on with what it was doing or stops to service the
device or program that caused the interrupt. The computer needs to identify the interrupt type and also establish
the level of interrupt priority.
-Interrupts allow computers to carry out many tasks or to have several windows open at the same time. An example
would be downloading a file from the internet at the same time as listening to some music from a library.
Whenever an interrupt is received it needs to be serviced. The status of the current task being run first needs to be saved.
-The contents of the Program Counter (PC) and other registers are saved. Then the interrupt service routine (ISR) is
executed by loading the start address into the Program Counter (PC). Once the interrupt has been fully serviced, the
status of the interrupted task is reinstated (the contents of all the saved registers are then retrieved) and the process
continues.

4.1 Types of software and interrupts
4.1.3 Running of applications
Interrupts

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4.1 Types of software and interrupts
4.1.3 Running of applications
Interrupts

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4.1 Types of software and interrupts
4.1.3 Running of applications
Interrupts

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4.1 Types of software and interrupts
4.1.3 Running of applications
Interrupts

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4.1 Types of software and interrupts
4.1.3 Running of applications
Interrupts

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4.1 Types of software and interrupts
4.1.3 Running of applications
Interrupts

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4.1 Types of software and interrupts
4.1.3 Running of applications
Interrupts

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Learning Objectives

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4.1 Types of software and interrupts
4.1.3 Running of applications
Watch the video for Relationship between hardware, firmware and operating systems
https://www.youtube.com/watch?v=W2mwbb9_7D8

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4.1 Types of software and interrupts
4.1.3 Running of applications
Relationship between hardware, firmware and operating systems

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4.1 Types of software and interrupts
4.1.3 Running of applications
Relationship between hardware, firmware and operating systems

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When a computer starts up, part of the operating system needs to be loaded into RAM – this is known as booting up the
computer (or a bootstrap loader).
The start-up of the computer’s motherboard is handled by the basic input/output system (BIOS). The BIOS tells the
computer where the storage device that holds the operating system can be found; it then loads the part of the
operating system that is needed and executes it.
The BIOS is often referred to as firmware. Firmware is defined as a program that provides low level control for devices.

The BIOS program is stored in a special type of ROM, called an EEPROM (Electrically Erasable Programmable ROM).
EEPROM is a flash memory chip, which means its contents remain even when the computer is powered down. However,
it also means the BIOS can be rewritten, updated or even deleted by a user.

However, while the BIOS is stored on an EEPROM, the BIOS settings are stored on a CMOS chip (Complementary Metal
Oxide Semi-conductor). The CMOS is powered up at all times via a rechargeable battery on the motherboard. Therefore,
the BIOS settings would be reset if the battery was removed or disconnected for some reason. Once the CMOS is re-
started, it will access the same BIOS program from EEPROM, but the settings will now be the default factory settings.
Consequently, if a user has changed the BIOS settings (for example, the clock speed), the settings will revert to those
settings made at the factory once power is restored to the CMOS.

4.1 Types of software and interrupts
4.1.3 Running of applications
Relationship between hardware, firmware and operating systems

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4.1 Types of software and interrupts
4.1.3 Running of applications
Relationship between hardware, firmware and operating systems

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4.2 Types of programming language, translators and integrated development environments (IDEs)

4.2.1: High-level languages and low-level languages

https://www.youtube.com/watch?v=O8-XzWy2JtA

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4.2 Types of programming language, translators and integrated development environments (IDEs)
4.2.1: High-level languages and low-level languages

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4.2 Types of programming language, translators and integrated development environments (IDEs)
4.2.1: High-level languages and low-level languages

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4.2 Types of programming language, translators and integrated development environments (IDEs)
4.2.1: High-level languages and low-level languages

Differences between high-level and low-level languages

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4.2 Types of programming language, translators and integrated development environments (IDEs)
4.2.1: High-level languages and low-level languages

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4.2 Types of programming language, translators and integrated development environments (IDEs)
4.2.1: High-level languages and low-level languages

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4.2 Types of programming language, translators and integrated development environments (IDEs)
4.2.2: Assembly languages

https://www.youtube.com/watch?v=ZcvcrLyQTVs

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4.2 Types of programming language, translators and integrated development environments (IDEs)
4.2.2: Assembly languages

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4.2 Types of programming language, translators and integrated development environments (IDEs)
4.2.2: Assembly languages

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4.2 Types of programming language, translators and integrated development environments (IDEs)
4.2.2: Assembly languages

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4.2 Types of programming language, translators and integrated development environments (IDEs)
4.2.3: Compilers and interpreters

https://www.youtube.com/watch?v=_C5AHaS1mOA

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4.2 Types of programming language, translators and integrated development environments (IDEs)

4.2.3: Compilers and interpreters

https://www.youtube.com/watch?v=c1nisKE8ln4

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4.2 Types of programming language, translators and integrated development environments (IDEs)
4.2.3: Compilers and interpreters

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4.2 Types of programming language, translators and integrated development environments (IDEs)
4.2.3: Compilers and interpreters

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Differences between Interpreter and Compiler:

4.2 Types of programming language, translators and integrated development environments (IDEs)
4.2.3: Compilers and interpreters

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4.2 Types of programming language, translators and integrated development environments (IDEs)
4.2.4: Integrated development environments (IDEs)

https://www.youtube.com/watch?v=kea1M_DUV1o

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4.2 Types of programming language, translators and integrated development environments (IDEs)
4.2.4: Integrated development environments (IDEs)

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4.2 Types of programming language, translators and integrated development
environments (IDEs)
4.2.4: Integrated development environments (IDEs)

An integrated development environment (IDE) is a software application that provides
comprehensive facilities to computer programmers for software development. An IDE normally
consists of at least a source code editor, build automation tools and a debugger. Some IDEs, such
as NetBeans and Eclipse, contain the necessary compiler, interpreter.

IDEs usually have these features:

» code editors
» a translator
» a runtime environment with a debugger
» error diagnostics
» auto-completion
» auto-correction
» an auto-documenter and prettyprinting.

Let’s look at each of these features in turn and see how they help the development process.

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4.2 Types of programming language, translators and integrated development
environments (IDEs)
4.2.4: Integrated development environments (IDEs)

1 - Code editor:

A code editor allows a program to be written and edited without the need t use a separate text editor. This speeds up the
program development process, as editing can be done without changing to a different piece of software each time the
program needs correcting or adding to.

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What is Code Editor

4.2 Types of programming language, translators and integrated development
environments (IDEs)
4.2.4: Integrated development environments (IDEs)

2 - Translator:

Most IDEs usually provide a translator, this can be a compiler and/or an interpreter, to enable the program to be executed.
The interpreter is often used for developing the program and the compiler to produce the final version of the program to
be used.

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What is Translator

4.2 Types of programming language, translators and integrated development
environments (IDEs)
4.2.4: Integrated development environments (IDEs)

3 - A runtime environment with a debugger:

A debugger is a program that runs the program under development and allows the programmer to step through the
program a line at a time (single stepping) or to set a breakpoint to stop the execution of the program at a certain point in
the source code. A report window then shows the contents of the variables and expressions evaluated at that point in the
program. This allows the programmer to see if there are any logic errors in the program and check that the program works
as intended.

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What is A runtime environment with a debugger

4.2 Types of programming language, translators and integrated development
environments (IDEs)
4.2.4: Integrated development environments (IDEs)

4 - Error diagnostics and auto-correction:

Dynamic error checking finds possible errors as the program code is being typed, alerts the programmer at the time and
provides a suggested correction. Many errors can therefore be found and corrected during program writing and editing
before the program is run.

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What is Error diagnostics and auto-correction:

4.2 Types of programming language, translators and integrated development
environments (IDEs)
4.2.4: Integrated development environments (IDEs)

5 - Auto-completion:

Code editors can offer context-sensitive prompts with text completion for variable names and reserved words.

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What is Auto-completion:

4.2 Types of programming language, translators and integrated development
environments (IDEs)
4.2.4: Integrated development environments (IDEs)

6- Prettyprinting:

Prettyprint refers to the presentation of the program code typed into an editor. For example, the
Python IDLE (see Figure below) automatically colour-codes keywords, built-in function calls,
comments, strings and the identifier in a function header. In addition, indentation is automatic.
.

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Open Ended

What is Prettyprinting