CS 117 Spring 2002

Review for Exam 2

March 6, 2002

open book, 1 page of notes

Material Covered

• Hanly– Chapter 3

– Chapter 4

– Chapter 5

• Friedman-Koffman– Chapter 3

– Chapter 4

– Chapter 5

– Chapter 6

Boolean Expressions

• needed for both selection and repetition• don't confuse == with =

a==b has value of either true or falsea=b has same value as b

• de Morgan's laws!(p && q) == !p || !q!(p || q) == !p && !q

Boolean Operators

• comparison operators < less than<= less than or equal>= greater than or equal> greater than== equal!= not equal

Boolean operators

• unary! logical

NOT

• binary operators&& logical and|| logical or

• short circuit evaluation

Selection Review

• Hanly Chapter 3– p 84 #1-4

– p. 92 #1-2

– p. 94 # 1-3

– p 105 # 1-5

• Friedman-Koffman Chapter 4– p 186 # 1-2

– p 210 #3

– 215 #1-2

– p 220 #8-12

Selection

• select between several alternative blocks of code

• two types– if else– switch

Selection

• selective execution of parts of the program

• ifif (condition)

statement;• condition is a boolean expression• statement is single statement or block of

statements enclosed by {}

if..else

if (condition)thenDoThis;

elsedoThat;

thisAlwaysDone;

• body of if and else one statement unless { } used

Multiple if statements

• Sometimes there are more than two cases. if (condition)

thenDoThis;else if (condition2)

doThat;else if (condition3)

…else

doInAllOtherCases;thisAlwaysDone;

format of switch

switch (variable) {case value1:

action1:break;

case value2:action2;break;

default: // if no other case holdsdefault action;

}

switch statement

• The first case for which variable has the value given in the case is executed

• break forces exit from the switch statement; without it, execution falls through to next case

switch example

• Suppose you want to write a simple calculator program. Your program will read in a character into the variable op and two numbers v1 and v2. You want to use a switch statement to decide what to do with v1 and v2. Provide cases for +, -, / and *, using the first case as a model.

code

switch (op) {case ' % ': ans = v1 % v2; break;

default: cout "error\n";}

case '+': ans = v1 + v2; break;

case '-': ans = v1 - v2; break;

case '*': ans = v1 * v2; break;

case '/': ans = v1 / v2; break;

Repetition Review

• Hanly Chapter 4– p 116 # 1-3

– P 125 # 1-5

– p 134 #1, 5

– p 140 #2

• Friedman-Koffman Chapter 5– p 232 # 2-5– p238 # 1-2– p 245 # 1, 2, 4-6– p 265 #1-2– p 268 #1-2– p 273 #2-3– p274 #1– p 284 #1-5, 7-10– p 285 # 6-7

Repetition

• executing same block of code multiple times

• three forms– while– do - while– for

Loop Review :while

• Most commonly used when repetition is not counter controlled

• condition test precedes each loop repetition• loop body may not be executed at all

while (condition) dothis;

Loop Review: do-while

• Convenient when at least one repetition of loop body must be ensured

• test condition after execution of body

dothat;

while (condition);

Loop Overview

• Counting loop - number of repetitions – known ahead of time – can be controlled by a counter

• also convenient for loops involving non counting loop control with simple initialization and updates

• condition test precedes the execution

for (initialization; condition; modification)doSomething;

Function Review

• Hanly Chapter 5

– p 165 # 1-4

– p 179 # 1-2

– p 185 #1-2

– p 188 # 1-2

• Friedman-Koffman Chapter 3 & 6– p 119 #1

– p 142 #1

– p 165 #10 (just write the functions)

– p 305 #3

– p 313 # 1

– p 337 #1, 5

Functions

• know the difference between a declaration and a definition

• know how and when to use void

• understand the difference between pass by value and pass by reference

• reference parameters

Function Declarations

• also called prototype or signature

• can declare a function without knowing how to write the function

Parts of a declaration

double someFunction( int param1, int param2);• The return type of the function is double. It can

be any type, either built-in or a class type. If nothing is to be returned, it should be void.

• The function name is someFunction. – The rules for naming functions are the same as for

naming variables.

• The parameter list is contained within the parentheses. There– can be any number of parameters, including 0.

Calling a function

• You call a function by giving its name followed by a list of arguments in parentheses. double x = someFunction( arg1, arg2);

• The list of arguments should match the function's parameter list in number of arguments and type.

• arg1 and arg2 may be variables, numbers or expressions. They are evaluated and the values stores in the corresponding function parameters.

Function Definition

• The function definition contains the code that is executed when the function is called.

double someFunction( int param1, int param2) {// code that is executedreturn aDouble; // required for function that returns a value}

• Note: param1 and param 2 are declared in the function signature; don't redeclare them or they will be hidden by the newly declared variables.

• The function parameters are places to store the values that are passed in.

• void functions return no value - don't use them with assignment

Value and Reference Parameters

• by default function arguments are passed by value – they can't be changed by the function

• reference parameters have a & between the type and the argument namevoid swap( int & a, int & b);

• Reference parameters can be changed by the function.