Transcript Computer Systems - Shawlands Academy

Outcome 2 – Computer Software
The Range of Software Available
• The Different Categories of Software
• System Software
• Programming Languages
• Applications Software
2 – System Software
2.1 -The Operating System
• Manages the hardware & communicates
with the user.
• O/S is broken down into layers so updates
can be written for specific layers.
• Some parts of O/S held in ROM chips, but
most parts held on disk – can be corrupted.
• Bootstrap program runs on start-up and
loads in the rest of the O/S from disk.
Operating System Layers
I/O
Kernal
2 – System Software
2.1.1 –Single-user Operating System
• The tasks of a single-user operating system is to
manage all the resources of a computer system.
• The main resources are.
– File management.
Memory management.
Command language interpreter.
Input - Output System
Process Management
2 – System Software
Single-user Operating System -Command
Language Interpreter
• The operating system takes user commands from
the keyboard and mouse.
• Passes them to the operating system which;
– Carries out the command.
– If command cannot be understood an error is reported
and a suitable message given back to the user.
2 – System Software
Single-user Operating System -File management
• The operating system supervises the creation, deletion
and updating of files on backing storage
• A directory keeps track of where files are stored.
This is a hierarchical directory structure in which files are
placed in folders (directories) and sub-directories
2 – System Software
Single-user Operating System -Memory
management
• The operating system decides where programs
and data are to be placed in main memory
• It also keeps track of what stage a program is at
and this applies equally to the operating system's
own memory space.
• If corrupted it could cause the computer to crash
2 – System Software
Single-user Operating System - Input-Output
System
• Peripherals all work at different speeds
• The I/O system hides the differences and it
makes them all appear to operate in a similar
manner.
• The I/O system does all the actual data transfers
and issues the appropriate control signals to the
peripherals.
• Manufacturer usually supplies software (called a
driver) for the user to install on their hard disk.
2 – System Software
Single-user Operating System - Process
Management
• O/S decides which tasks get to use the
processor
• Processor management is often called the
Kernel of the system
• It is the core function of the OS 11 File
management
2 – System Software
2.1.2 Network Operating System
• All Stations should have the same O/S to use the
network system and to share messages on the
network system.
• Multi-User Access – Operating System must
provide a “logging-on” procedure with passwords
for security.The user ID controls what the user
has access to on the network.
• File Attributes – A user usually has read/write
(r/w) access to their own files, read-only access to
shared files.
2 – System Software
2.1.2 Network Operating System
• File and Print Services – different users
have different levels of access.
• Data Sharing and Integrity –. Only one user can
edit a shared file at any one time (locking-out
system).
2 – System Software
2.2 Utility Programs
• Utility programs aid the maintenance of the
computer or make the user’s life easier.
• Includes disk formatter, disk tools and
defragmentation tools.
– Files are saved wherever the system can find space in
consecutive sectors. As files are added and deleted
spaces become available and are all over the filing
system. A de-fragger moves files around to create a
contiguous system with no empty sectors.
2 – System Software
2.3 Translators
• A Translator turns a program written in a highlevel language into machine code.
• The high-level language is the source code and
the machine code is the object code.
• Compilers – translate the source code in one go
and produces executable machine code.
• Interpreters – Translate and execute a program
line by line. Interpreted programs run much
slower than compiled. Interpreter is simpler to
learn and use.
4 – Application Software
4.1 Types of Applications
• You need to be aware of applications which
handle:–
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Text (word processor, web browser)
Number (spreadsheet, accounts package)
Data (database, world wide web)
Communications (e-mail, file transfer)
Graphics (painting, drawing, CAD)
Multimedia (sound, video)
Integrated Packages (Works v Office)
4 – Application Software
4.2 Features and Requirements
• All application packages have features which distinguish
them e.g.
– Database – search and sort data, print reports.
– Multimedia – allows user to create presentations using sound and
video.
• Application packages have minimum hardware
requirements.
– Memory – Minimum RAM used is specified.
– Hard Disk – Minimum disk space for installation and running
usually specified.
– Processor and operating system.
– Any specific peripherals.
4 – Application Software
4.3 Standards
• Each application package saves files in its
own way. Standards set ways of saving
data so other packages can read the data.
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SYLK, standard for spreadsheets
RTF, standard for text
CSV, comma separated variable for database
JPEG, GIF, TIFF, for graphics