1. Chapter 48 Operating Systems, Computer Architecture and Databases
Prepared by: M206 Team - Kuwait Branch

2. Team Work - Kuwait Branch
Objectives
Understand and use the terminology of computer architecture and database technology.
Describe in approximate terms the architecture of a typical personal computer.
Describe how layers of system software are used, especially in the form of an operating system.
Summarize the data handling requirements of large organizations and indicate some of the features that mainframe computer systems must offer to meet these requirements.
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System software
System software is a software that helps the computer carry out its basic operating tasks.
System software is at a very low level: linked to the precise components and structure of the computer.
System software is not concerned with abstractions like bank accounts or aircraft flight plans, but with locations in memory, registers in chips, and so on.
There are two main categories of the system software:
Operating system.
Utilities: are means whereby users interact with an operating system.
Certain utilities are assumed to be part of the operating system.
For example, a utility that allows you to view files and folders might automatically be started by the operating system.
Some utilities can be purchased separately to extend the functionality of the operating system.
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Operating systems
Operating system is a piece of system software that is used to manage and coordinate the use of computer’s resources.
The five basic functions of an operating system are to:
Control basic input and output;
Allocate system resources;
Manage storage space;
Detect equipment failure;
Maintain security.
Operating system is designed to work only on certain specific kinds of machine configuration.
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Operating systems
Machine configuration is the specification of a computer in terms of various key hardware attributes, including:
The make and the model of processor.
Other chips in the computer.
The capacity and speed of the memory and disks.
Type and speed of the bus systems.
Higher level of abstract (Architecture of a computer)
By architecture we mean a design based on a family of computers that have compatible memory, disk and bus designs.
Labeled by the processor on which they are based or by the operating system they support. (e.g. Pentium V, Windows NT)
Currently, the most abstract view we have of computer systems is in terms of ‘platforms’
A platform is a set of architectures based round a family of processors, such that software designed for a specific platform can run more or less unchanged on any computer system of that platform.
e.g. IBM PC platform, Unix Platform.
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Operating systems
Operating systems could be multi-user and multitasking.
A multi-user operating system is the operating system that allows several people to work at the computer at the same time.
A multitasking operating system is the operating system that allows programs to run in parallel.
e.g. UNIX and Windows NT.
Operating systems are designed for one particular platform (architecture or computer) and cannot be moved to another platform, which raises the problem of portability.
The basic problem of portability is that hardware is immutable, once manufactured and assembled you cannot change its range of behavior.
However, you can change software, which is malleable, although not trivially so.
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Operating systems
The solution of portability is layering: a computer system can be regarded as being composed of layers of software and hardware.
A layer of system software may be interposed between hardware components, between software and hardware components, and even between software components, in order to smooth out differences between the components by acting as a mediating layer.
Example: a printer device driver provides a common protocol (a mediating layer) for applications that need to print.
Computer systems are divided into three interacting layers: Application software, operating system and hardware.
The operating system forms a mediating layer between the application software and the hardware, as shown in Figure 1.
Because an operating system is usually designed to work with a particular hardware platform, the application writer does not have to worry about the characteristics of individual hardware components, which are many, but only about those of the operating system, which are relatively few.
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Operating systems
Downward compatibility: new version of an operating system may be able to run an application designed for an older version.
This is not always the case! A new operating system may be quite incompatible with its predecessor.
Example, although both MS-DOS, Windows 3.1 and Windows NT can run on the same PC (Wintel) platform, programs that run under one of these operating systems will not necessarily run under the others because the operating systems deal with the same hardware in quite different ways.
An emulator is a layer of software interposed between an application that is designed for a certain operating system and the different incompatible operating system of the computer being used.
The emulator typically translates commands made by the application to its anticipated operating system into commands to the actual operating system being used.
Thus an emulator is a translation utility.
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9. Computer architecture Memory, CPU, I/O
Physical memory (RAM) has a very fast access time (100,000 times faster than hard disk).
The more RAM a computer has, generally the faster it can process data and run applications.
Virtual memory is one of the means developed to overcome the problems that arise when a computer’s configuration is at variance with the requirements of the software.
With virtual memory, the computer can look for areas of RAM that have not been used recently and copy them onto the hard disk.
This frees up space in RAM to load the new application.
Because it does this automatically, you don't even know it is happening, and it makes your computer feel like is has unlimited RAM space
Applications using virtual memory operate more slowly than those using physical memory.
Virtual disk is a means of improving disk performance, whereby a computer system allocates some RAM (which has a much faster access time than a hard disk) to be ‘set aside’ to supplement the storage function of the hard disk.
The computer system then benefits from very fast apparent disk performance.
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10. Computer architecture Memory, CPU, I/O
Central processing unit (CPU) is the heart of the computer that includes the following elements:
Processor’s manufacturer ( Ex: Intel or Motorola).
Word size (Ex: 8,16,32,or 64-bit).
Instruction set (Ex: complex instruction set computer ,CISC or reduced instruction set computer, RISC).
Method of processing (Ex: serial or parallel).
Clock rate.
Cache.
Input/output (I/O) are peripheral devices that act as interfaces between the computer system and the user.
e.g. Graphic card, network card, modem card, sound card,…etc.
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The Boot process
When the computer is switched on, the boot process starts up immediately and prepares the computer for use.
When you apply power to your pc, it activates the instructions stored in ROM, which perform some self-tests on the computer before loading the operating system from the hard disk.
Once loaded into RAM, the operating system takes over.
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12. Large computer systems
An example of an application that can run on large computer system the Airline Reservation application.
An example of a physical large computer system is the mainframe computer which is very powerful and can serve as the center of a complex computing operation.
Large computer systems should have the following properties:
Fault-tolerant: No breakdown, Back-up system is always ready.
The could be done by having at least two mainframe computers identically configured, and two sets of disks with identical copies of the data on them, always available.
In the event of one system failing or needing maintenance the operator brings the backup system ‘online’.
Deadlock free:
Deadlock is the case in which lot of applications queue up to use a computing resource that never became available.
The operating system detect deadlock and prevent it from happening.
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13. Dealing with large amounts of data
A database can be used to organize and structure a large amount of data so that it can be easily searched, manipulated and updated.
There are different types of database system that can be used to model the relationships between data,
But relational databases are the most common.
Relationships between entities in traditional database technology are similar to, but not the same as, associations between objects in object technology.
Information can be retrieved from a database by using queries that specify the search criteria in terms of:
The relevant field name(s);
The required condition(s);
And often, one or more logical operators (such as AND, OR and NOT).
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14. Dealing with large amounts of data
This is a brief comparison between traditional database terms and the object-oriented terms we have been using in the course.
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