Database Systems: Design, Implementation, & Management, 5 th Edition, Rob & Coronel 1 A. HARDWARE Hardware is the part of the computer that we can see and touch.

Hardware Any computer must perform 4 basic Functions; –Input (We enter data into the computer) –Processing (The computer does something with the data) –Output (The computer gives us the result) –Storage (If we want to save our data we transfer it to a disk) To perform each of these functions, there must be pieces of Hardware, called Hardware Devices.

Hardware Devices Input Devices;Keyboard and Mouse Processing;CPU – Central Processing Unit (Contains ALU – Arithmetic-Logic Unit and CU – Control Unit) Output Devices;Monitor and Printer Storage Devices(a) Temporary: RAM(Main Memory) and (b) Permanent: Hard Disk&Diskette

Hardware Devices & Functions

Why do we have 2 types of data storage? Data passing through RAM moves at “the speed of electricity”, it is extremely fast. We need this speed to run our programs. But RAM is only for temporary data storage… when the power is turned off all the data in RAM is erased.. it is lost! We must also have permanent storage, so we don’t lose our data and programs.

Why do we have 2 types of disks for permanent storage? The Hard Disk is fast and stores large amounts of data (files and programs) –4 to 10 billion characters of information It is fixed inside the System Unit –We can not see it, touch it or remove it The Diskette is very slow and stores small amount of data –Only 1.4 million characters of data It is removable, we can use a diskette to carry information from one computer to another.

PC Storage Hardware In Our Teaching Labs Storage TypeStorage CapacityFeatures RAM (Random Access Memory) 32 million or 64 million characters Temporary electronic storage. Data is lost when power is off. No moving parts. Extremely fast Hard Disk Drive C: and D:4 to 10 billion characters About 1 to 3 million typed pages like this page. Large, Permanent storage Mechanical. Very fast. Disk is Fixed (Not portable) Diskette Drive A: 3½ Floppy – HD (High Density) 1.44 million characters About 250 typed pages like this. Small Permanent storage. Mechanical. Very SLOW Removable diskette (Portable)

Database Systems: Design, Implementation, & Management, 5 th Edition, Rob & Coronel 8 B. SOFTWARE Software are the programs that run the computer

Software The computers use 3 main types of Software Packages: –Application Packages: Pre-written programs that PC users use to do productive work. There are 2 main types: General Application Software Packages (Word,Excel,CAD,etc.) –Useful to people working in all types of organizations Industry Application Packages (Fidelio,Galileo,etc.) –Created for specific industries (banks,retailers,insurance comp.) –Programming Languages: Used by programmers to create Application Packages (Visual Basic,C++,Cobol,Pascal,etc.) –Operating Systems:The programs that run the computer. (MS-DOS, Windows, Unix, etc.)

Functions of Disk Operating Systems (DOS) DOS performs two important functions: DOS manages the hardware… –i.e. it moves the data from the keyboard to RAM, from RAM to the disks or to the monitor. –DOS does this work automatically. DOS helps us manage our information (data or programs) which are stored on the disks in files… –DOS can not do this work automatically.. We have to tell DOS what we want to do with our data. –In order to tell DOS what we want it to do with our data, we need to learn 2 things; How DOS organizes data stored on disks. How to “tell” DOS what we want it to do.

Data Organization & Storage Our information (data and programs) is stored permanently on the disks in FILES. Since we have thousands of files, they must be stored in many separate areas of disks, so that we can easily find. These separate areas are called FOLDERS – an empty storage area into which we can put our files. DOS organizes the FOLDERS on the disk into a hierarchy. At the top of the disk hierarchy is a folder that is always called the ROOT folder. DOS creates the ROOT folder (when we format a disk) The symbol \ refers to the Root folder All the other folders must be created and named by us

Hierarchical Folder Structure On a Disk A: Excel YR9 9 Games Word Memos List DOS Fidelio Other  The chart shows the folder structure on a diskette  Folders are not data; storage areas on the disk  Any folder may have many sub-folders, but each folder can only have one PARENT folder

PATH – Folder and File Addresses Our data is contained in files, and these files are stored on the disks in folders. The folders are then arranged into a hierarchy. This hierarchy allows each folder (and File) to have a unique address on the disk. The address is called the Path to the file or folder

Path The Path is just a simple description of the direction to travel from the top of the hierarchy to the file or folder. Note that after the Disk name A: (or C: or D:) the \ is shorthand for Root Folder, but after a folder name, the \ is just used as a name separator. A: \ Word \ Lists \ Section-1.doc A : Backslash Word Lists Section-1.doc [Floppy Disk] [Root Folder] [Folder name] [Folder name] [Name of the file]