Unit 4 Review
Unit 4A – Software Overview
Software
· A set of instructions that tell a computer how to perform a specific task
· Consists of many types of files that all work together
o A .exe file is a program; the main executable file
o A .dll file is an executable that supports the main executable
o Graphics file such as .ico, .gif, .pcx, and other types contain images
o Help text in .txt or .hlp file extensions
o Data files in .dat extensions
o And many other types
· Most software provides a task-related environment on the display screen.
Source Code, Object Code, Compilers, and Interpreters
· A processor only executes its instruction set represented in machine language
· Most programmers use high-level languages
o More English-like easier to use
o Allows for complex instructions well above machine language level
· C, C++, Java, Visual Basic, and COBOL are some high-level programming languages.
· A program written in a high-level language is called source code.
· Source code must be converted to machine language to be executed This conversion process is done by a compiler or interpreter.
· A compiler converts the instructions in a source code program as a group and saves the resulting machine language instructions in an executable file called object code.
· An interpreter converts instructions in a source code program line by line and sends those instructions directly to the processor. The resulting machine language isn’t saved (no object code) so the interpretation step is done every time the program is executed.
· Machine language programs use the instruction set of a given type of processor
o So a machine language program only works on a given type of processor
o May be able to use the same high-level language program on multiple platforms by re-compiling source code to object code on the new platform
Software Categories
· Software is divided into two main categories, system software & application software.
· System software tells the computer how to carry out its basic operating functions and manage internal operations
· Application software carries out a task for a user.
· System software consists primarily of operating systems but also device drivers, utilities, and programming languages
Unit 4B – Operating Systems
An operating system is the master controller of all activities on the computer.
Application programs use services provided by the OS to help carry out its tasks.
The OS manages the resources of the computer.
A FIFO scheme (first-in, first-out) is often used to allocate scarce resources
Resources include the processor, memory, storage, and peripheral devices.
The OS also defines a standard look and feel that application programs usually follow.
A GUI or graphical user interface provides menus, icons, and a mouse.
A command line interface requires the user to remember various commands.
A bootstrap program is initiated from ROM to load the OS into RAM at power-up.
If computer is on, OS is always an active task and requires RAM and processor resources
Users don’t usually interact directly with the OS except when:
· Launching programs (clicking on an icon or selecting a menu option)
· Managing files (uses Windows Explorer or My Computer)
· Using help
· Customizing the user interface (Control Panel)
· Configuring equipment (usually done automatically by OS using Plug and Play)
Types of Operating Systems
Single-user – expects to deal with one set of input and output devices for one user.
Multi-user – allows one computer to deal with processing needs of many users at once.
Multi-tasking – manages processor and RAM so multiple programs can be used at once.
Windows – PC operating system running on platforms with Intel or AMD processors
· Uses a GUI interface
· Easy to learn for novice users
· Tremendous amount of application software available
· Resource hog; significant computer resources required to use Windows
Mac OS – PC operating system running on the Macintosh platform (Apple)
Linux – open source operating system available for free under a general public license
· uses a command line interface
· requires more technically capable users
· far less application software available than for Windows
· Often used for web servers and scientific applications
· Can be used to extend life of an outdated computer due to minimal resource needs
Proprietary – something that is owned by an individual or company
Open source – source code is available so the user can modify the software
General public license – free software, users can copy and distribute as they choose.
Our lab computers use Windows which is a single-user, multi-tasking operating system.
Microsoft Office Application Software
Word Processing Software (Word)
Key features of word processing software:
· Word wrap
· Spell checking
· Grammar checking
· Thesaurus
· Search and replace
· Integration of graphics and pictures
· Page headers and footers to appear at the top or bottom of each page
· Tables to align columns of data
· Specify formatting features such as
o Font
o Paragraph styles such as margins, tabs, indents, line spacing, and horizontal alignment (left, right, center, justified)
o Page layout such as headers, footers, page numbering, graphics, pictures, tables, and vertical alignment (top, bottom, center, and justified)
Spreadsheet Software (Excel)
A row and column approach to data representation and numerical problem solving
Each row and column intersection is a cell
Used to record table based data and do what-if analysis
A cell can hold a value (number), a label (text), a date, or a formula
A formula contains instructions on how to use the contents of other cells in a calculation
Formulas use cell references (B2, D4, etc) mathematical operators (add, divide, etc)
Formulas also allow use of built-in functions such as Sum, Average, Min, Max, If, etc
Whenever the contents of a cell are changed, all other cells are automatically recalculated
Database Software (Access)
A record contains data for a single person, place or thing
You, for example, are a record in the Haywood Community College database
A field holds a single piece of data about a record, such as a name or phone number
A table holds all the records for a group of things such as customers or vendors
A Database usually refers to a collection of tables
A relational database allows relationships to be defined between tables.
Relational databases tend to use the terms column for a field and row for a record
A field can be defined to hold text, numeric, date, currency, or Yes/No data
Database management software (DBMS) allows users to sort and select data
Query languages such as SQL provide the ability to locate, manipulate, and display data