systems software & operating systems. computer languages
TRANSCRIPT
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Systems Software&
Operating systems
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Computer Languages
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Programming languages All software is
written in special programming languages.
The CPU of the computer can only understand it’s own language – zeros and ones.
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Programming languages Programming languages are broken
down into: Low Level Language High Level Language
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Low Level LanguageMachine Code
All instructions in every program must be translated into the computers own language called Machine Code
Machine Code uses commands that we do not necessarily understand as humans
It uses binary numbers to represent commands
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Machine Code Example
111111111111111111111111
000000000000000000000000
101010101010101010101010
010101010101010101010101
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Machine Code - Advantages:
Because this is the computers own language:- programs do not need to be
translated therefore, programs run very fast
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Machine Code - Disadvantages
Difficult for humans to program in Machine Code
Difficult to locate errors (DEBUG)
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High Level Language
A computer language that uses commands similar to the English Language
True Basic Comal Pascal Fortran Prolog
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Advantages: HLL
Easier to read, understand and write programs
Easier to locate errors (Debug)
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Portability: A Program is portable if it can run on
different Operating Systems or Platforms
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Disadvantages: HLL
Instructions written in a HLL must be TRANSLATED into machine code before the CPU understands the instruction
This takes time making the program slower to run
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Translator Programs
Programs which will translate the instructions of a program into Machine code.
There are 2 types of translator: Interpreter Compiler
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Source and Object Code Source code is the list of
instructions written in a High Level Language
Object Code is the translated version of the instructions written in Machine Code
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Interpreter
Translates the instructions of a program written in a HLL into Machine code one instruction at a time.
LET TOTAL = 0LET TOTAL = 0 FOR COUNTER = 1 TO 10
0000011110101000011010101100000111101010000110101011PRINT “PLEASE ENTER NUMBER”
INPUT NUMBERLET TOTAL = TOTAL+NUMBER
NEXT COUNTERPRINT “THE TOTAL IS “;TOTALEND
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Note: Interpreter
Easier to learn to program as errors
are identified as commands are entered Changes are made easily Runs slower Must have the interpreter loaded into memory
for the program to run (requires more memory).
Does not produce Object Code
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Compiler
Translates the instructions of a program written in a HLL into Machine code in a single operation.
LET TOTAL = 0 000001111010100001101010111
FOR COUNTER = 1 TO 10 101010101010101010101010101
PRINT “PLEASE ENTER NUMBER” 000111000111000111001110010
INPUT NUMBER 111111111111111111111000000
LET TOTAL = TOTAL+NUMBER 111111110000000000000000000
NEXT COUNTER 111111111111000000000011111
PRINT “THE TOTAL IS “;TOTAL 000000000011111111100000001
END 111100001110001110001110001
SOURCE CODE OBJECT CODE
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Note: Compiler
Changes are not easily made. The original source code will have to be edited
and translated again Runs fast Produces Object Code which can be run
without the compiler being present in memory - efficient
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Classwork Questions1. Why do HLL's need translation? 2. How do translators help programmers? 3. State two common features of all HLL's. 4. Name two types of translator. 5. Describe how an interpreter works 6. Describe how a compiler works. 7. What are object and source code? 8. If someone were just learning how to write programs, which type of
translator would you recommend they use? (Give two reasons to justify your answer)
9. By considering a compiler and interpreter, which type is more efficient? (Give two reasons to justify your answer)
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Revision - Types of FilesProgram files - software is another name for a program file
Program files are made up of instructions which the computer follows (Microsoft Office, Windows XP)
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Revision - Types of Files
Data files - The files you create using the software on the computer
These are files containing data which a computer user has created (Personal Profile, Dental Check up Database, Olympic Pentathlon Spreadsheet)
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Software A computer cannot work without
software All the jobs that a computer can do
are controlled by a program Different computers can have
different software installed but all computers must have:-
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An Operating System The Operating System is the set of
programs which controls the entire operation of the computer and any devices that are attached to it
The OS runs from the minute the computer is switched on until it is switched off
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Types of Operating System
Windows XP 98 95
MAC OS
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Functions of the Operating System
1. Memory Management
2. File Management
3. Error Reporting
4. Human Computer Interface
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Memory Management
This program in the Operating System controls where data and programs are placed in Main Memory
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File Management
This program in the Operating System deals with storing and retrieving files from backing store
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Error ReportingThis program in the Operating System deals with Letting the user know if any mistakes have occurred
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Human Computer Interface
This program in the Operating System provides a human computer interface for the user
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ROM and RAM The OS can be stored in ROM or RAM.
If stored on ROM chip the chip must be removed to update the OS
If stored in RAM it can be updated quickly and easily by overwriting with the new version of the OS
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Directory / Folder This is an area on backing storage where
files are stored
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Filing system
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Filing Systems There are 2 main types of filing system
Flat Hierarchical
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Flat Filing SystemThis system presents all file information in
one level1 Text File 1 5 Spreadsheet File 1
2 Excel File 1 6 Text File 2
3 Word Processing File 1 7 Database SS
4 Word Processing File 2 8 Spreadsheet File 2
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Flat (Disadvantages) Not user friendly Poorly organised Difficult to find files if the user forgets the
name of it Groups of files can’t be protected from
unauthorised users All files might not be able to be seen on the
monitor screen
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Hierarchical Filing System This system allows different levels to be set
up and presented
Files can be grouped together
Files are organised into Directories Sub-directories
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Text File 1 Text File 2 WP File 1 WP File 2SS File 2SS File 1
ClarisWorks SS ClarisWorks WP
HARD DISK
PROGRAM FILES DATA FILES
TEXT FILES SS FILES WP FILES
Root Directory
Sub-directories
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Hierarchical (Advantages) More user friendly Better organisation Files can have the same names provided
they are not in the same directory Directories can be protected from
unauthorised users Easier to find files (Is this a good thing?)
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Sequential Access to Data The data has to be accessed in
the order it is stored. Access is slow
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Random Access to Data The data has to be accessed in the
any order. Access is fast as we can go directly to the data required.
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Interactive Systems In an Interactive System the user and the
computer communicate, they interact, and the computer program responds directly to commands
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Interactive systems
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Real-Time system A Real-time system is an interactive system which
cannot afford to have a delay in the time taken for the computer to respond.
Response in a Real-time system is vital
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Background Job Capability
This is when the operating system carries out a task in the foreground and another task in the background. The processor is so quick the user thinks that the tasks are happening at the same time
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Background Job CapabilityExample
The computer can print a document as a background task while at the same time appear to allow the user to word process a document as a foreground task. The user does not have to wait on the print job finishing before continuing to word process a document.
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Device DriversA device driver is a program which is an add-on to the operating system in a computer, to allow the computer to operate a particular device which is attached to it
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Printer DriversA Printer driver is a program which is an add-on to the operating system in a computer, to allow the computer to operate a particular printer which is attached to it
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Classwork Questions 21. Files can be stored on disc on a Flat filing system or a Hierarchical filing
system. Describe each system. (A diagram may be helpful in your answer)
2. Which type of filing system do you use for storing your computer files and why?
3. Draw a hierarchical representation of how you store your files on your computer system.
4. What is the purpose of system software?
5. Name two examples of system software.
6. Why might an operating system be thought of as the most important piece of software a computer uses?
7. Name the four functions of an OS.
8. Describe four functions of an OS
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End of Unit Check Up You can now try the Interactive Revision
exercise for this unit.