IT101-1 Exam

Hardware and Software

the two majors components of any computer system

Hardware

equipment, or devices (tangible parts)

Software

programs that contain instructions for the computer

Four major operations in a computer

• Input

• Processing

• Output

• Storage

Input devices

allow data to enter the computer

• ex. Mouse, keyboard, scanner

Central Processing Unit (CPU)

hardware that performs the tasks

Output devices

provide data to the user

• ex. Printer, monitor, speaker

Programming language

special language containing instructions for the computer

• ex. Visual Basic, Java, C#, C++, COBOl

Syntax

rules governing word usage and punctuation in the language

Machine Language

controls the computer's on/off cicuitry

Compiler or interpreter

software that translates programming languages to machine language

Understand the problem

• May be the most difficult phase

• Users may not be able to articulate their needs well

• User needs may be changing frequently

• Programmers may have to learn the user's Functional job tasks

Plan the logic

• Plan the steps that the program will take

• Use tools such as flowcharts and pseudocode

• Walk through the logic before coding by desk - checking the logic

Code the program

• Select the programming language

• Write the instructions

• Planning generally more difficult than coding

Use software to translate the program to machine language

programmers write instructions in high-level languages that resemble a natural language

Compilers or interpreters

change the programs into a low-level machine language

Syntax errors

are identified by the compiler or interpreter

Test the program

• Execute it with sample data and check results

• Identify logic errors and correct them

• Choose test data carefully to exercise all branches of the logic

Put the program into production

• Might mean simply running the program once

• Process might take months if program is used on regular basis or is part of larger development

Maintain the program

• Maintenance

• Common first programming job

• Make changes to existing programs

Documentation

supporting paperwork for a program

Conversion

entire set of actions organization must take to switchover to new programs

Prompt

• message displayed on a monitor

• Asks the user for a response

Command prompt

location to type entries to communicate with the operating system

Graphical User Interface (GUI)

allows users to interact with a program in a graphical environment

Flowchart

A pictorial representation of the logic steps

Pseudocode

• Natural language representation of the logic

• English-like representation of the lo

Flowlines

• Connect the steps

• Show the sequence of statements

• Have arrows to show the direction

Terminal symbol

Shows the start and end points of the statements

Oval

Start/end

Paralellogram

Input/Output

Rectangle

Process

Diamond

Decision

Infinite loop

• a sequence of statements that repeats forever with no escape

• avoid infinite loops by testing for a predetermined value that means "stop processing"

Decision

testing a value

Sentinel value

• Does not represent real data

• Signal to stop

• Can be used with input from files or from users

End-of-file(EOF) marker

• Code stored in the file that marks the end of the data

• Usually used instead of a sentinel value for file input

Flowchart connector symbol

• Marks a logic transfer to another location in the flowchart

• Transfer location can be on the same page or on another page

On-page symbol

a circle with a number or letter to identify the matching transfer location

Off-page symbol

a square with pointed bottom, containing page number and a number of letter to identify the matching transfer location (banner symbol)

Variable

A memory location whose contents vary; also called an identifier

Text

stored by string, text, or character variables

Numeric

stored by numeric variables

Constants

• Values that do not change while the program is running

• Have identifiers, and can be used like variables for calculations, but cannot be assigned new values

Integer

Whole numbers only

Floating-point

fractional numeric values with decimal points

Procedural programming

focuses on the procedures that programmers create

Object-oriented programming

focuses on objects that represent real-word things and their attributes and behaviors

Data Items

• All the text, numbers, and other information that are processed by a computer

• Stored in variables memory

Declaration

Statement that provides a data type and an identifier for a variable

Identifier

Variable's name

Garbage

Variable's unknown value before initialization

Camel casing

Variables names such as hourlyWage have a "hump" in the middle

Magic number

• Unnamed constant

• Purpose is not immediately apparent

• Avoid this

Spaghetti code

Snarled program logic

Sequence

• Perform actions in order

• No branching or skipping any task

Selection (decision)

• Ask a question, take one of two actions

Dual-alternative or single-alternative ifs

Loop

Repeat actions based on answer to a question

Priming read (or priming input)

• Reads the first input data record

• Outside the loop that reads the rest of the records

• Helps keep the program structured

Dual-alternative (or binary) selection structure

Provides an action for each of two possible outcomes

Single-alternative (or unary) selection structure

• Action is provided for only one outcome

• if-then

if-then clause

Holds the action or actions that execute when the tested condition in the decision is true

else clause

Executes only when the tested condition in the decision is false

Compound condition

Asks multiple questions before an outcome is determined

AND decision

• Requires that both of two tests evaluate to true

• Requires a nested decision (nested if) or a cascading if statement

Conditional AND operator

• Ask two or more questions in a single comparison

• Each Boolean expression must be true for entire expression to evaluate to true

Truth tables

Describe the truth of an entire expression based on the truth of its parts

Short-circuit evaluation

Expression evaluated only as far as necessary to determine truth

OR decision

Take action when one or the other of two conditions is true

Conditional OR operator

• Ask two or more questions in a single comparison

• Only one Boolean expression in an OR selection must be true to produce a result of true

Range check

• Compare a variable to a series of values between limits

• Use the lowest or highest value in each range

• Adjust the question logic when using highest versus lowest values