111/18/2015cs150 introduction to computer science 1 announcements i have not graded your exam yet

04/21/23 CS150 Introduction to Computer Science 1

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Announcements

I have not graded your exam yet


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Multiple Alternative Ifs

if (condition1)

statement1;

else if (condition2)

statement2;

…

else

defaultstatement;


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Program

Write a program that displays a letter grade corresponding to an exam score90 - 100 A

80 - 89 B

70 - 79 C

60 - 69 D

0-59 F


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Example

if (salary < 0.00)

tax = -1;

else if (salary < 15000.00)

tax = 0.15 * salary;

else if (salary < 30000.00)

tax = (salary - 15000.00)*0.16 + 2250.00;

else

tax = salary * 0.26;


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What’s the difference?

if (x >= 0)

x = x + 1;

else if (x >= 1)

x = x + 2;

if (x >= 0)

x = x + 1;

if (x >= 1)

x = x + 2;


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Selection Structure Review

Write a program to solve the following problem:A police department needs to calculate fees for speeding tickets.

The fees are as follows:Speed Fee

75 or greater $60.00

51 - 74 $40.00

36 - 50 $20.00


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Switch Statements

Another form of selection statement

Similar to if’s

Useful for lots of alternatives


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Example

switch (watts){

case 25: life = 2500;

break;case 40:case 60:

life = 1000;break;

case 75:case 100:

life = 750;break;

default:life = 0;

}


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Form

switch (selector){case label1: statements1;

break;case label2: statements2;

break;…case labeln: statementsn;

break;default: statements;

}


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Example

switch (musical_note)

{

case ‘c’:

cout << “do” << endl;

break;

case ‘d’:

cout << “re” << endl;

break;

case ‘e’:

cout << “mi” << endl;

break;

case ‘f’:

cout << “fa” << endl;

break;

case ‘g’:

cout << “sol” << endl;

break;

case ‘a’:

cout << “la” << endl;

break;

case ‘b’:

cout << “ti” << endl;

break;

default:

cout << “An invalid note was read.”;

}


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Important!

Selector must be ordinal type

Each possible value is a separate case

break stops statements for case, otherwise continue with statements for next case


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Example

switch (color){case ‘R’: case ‘r’:

cout << “red” << endl;case ‘B’: case ‘b’:

cout << “blue” << endl; case ‘Y’: case ‘y’:

cout << “yellow” << endl;}

What happens when color is ‘r’? ‘B’? ‘Y’?


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Example

switch (x > y){case 1:

cout << “x greater” << endl;break;

case 0:cout << “y greater or equal” << endl;break;

}

Write as if statement


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Questions

Can you write any switch statement as an if?

Can you write any if statement as a switch?


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Problem

Write a switch statement to convert a character digit to an integer


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Change to switch

if (speed > 35)

fee = 20.00;

else if (speed > 50)

fee = 40.00;

else if (speed > 75)

fee = 60.00;


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Examples

Write an if statement that prints out the level of schooling. (0, none; 1 through 6, elementary; 7 through 8, middle school; 9 through 12, high school; > 12, college)

Write a switch statement to do the same


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Write a Program

Input an integer

If the integer is positive, increment a variable poscount by 1.

If the integer is negative, increment a variable negcount by 1.

If neither, increment zerocount by 1.


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Unary Operators ++ and --

++ is increment operatorx++;

is the same as x = x + 1;

-- is decrement operatorx--;

is the same as x = x - 1;


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Prefix and PostfixUnary ++ and --Prefix Postfix

k = --x; k =x--;

k = ++x; k = x++;

Increment/ Assign value of x to

decrement x k, then increment

then assign or decrement x

value of x to k


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Example

cout << “Value of i is” << i;

cout << “Value of i++ is” << i++;

cout << “Value of ++i is” << ++i;

cout << “Value of --i is” << --i;

cout << “Value of i-- is” << i--;


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Program

Write a program that outputs the following:

*****

*****

*****

*****

*****


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count = 0;

while (count < 5)

{

cout << “*****” << endl;

count++;

}

How many times (iterations) does loop run?

Loops

Loop Control Variable

Initialize LCV

Change the value of count


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While loopswhile (logical expression is true)

statement;

while (logical expression is true)

{

statement1;

statement2;

…

}


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Key ingredients Initialize

MUST initialize loop control variable

TestThe value of loop control variable is tested during each

iteration of loop

UpdateLoop control variable is changed during each loop iteration

If any one of these is missing or incorrect, your loop won’t run properly--not at all, too many/few times or infinitely.


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Examples

Write a while loop that outputs each integer from 1 to 5 Write a program that inputs the following data for 5

students: name, id# and grade Write a program that inputs the following data for a user

specified number of students: name, id# and grade

111/18/2015cs150 introduction to computer science 1 announcements i have not graded your exam yet

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