Transcript REACH CECS 130 Final Exam Test Review

Do you know the syntax for each of these, used to read
and write to data files?
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Pointers: think of it as the memory address of the file
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fopen()
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fclose()
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fscanf()
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fprintf()
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fopen() returns a FILE pointer back to the pRead
variable
#include <cstdio>
Main()
{
FILE *pRead;
pRead = fopen(“file1.dat”, “r”);
if(pRead == NULL)
printf(“\nFile cannot be opened\n”);
else
printf(“\nFile opened for reading\n”);
}
Mode
Meaning
Already Exists
Does Not Exist
“r”
Open a file for reading
read from start
error
“w”
Create a file for writing
destroy contents
create new
“a”
Append to a file
write to end
create new
“r+“
Open a file for read/write
read from start
error
“w+“
Create a file for read/write
destroy contents
create new
“a+“
Open a file for read/write
write to end
create new
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Pretty basic.
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Reads a single field from a data file
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“%s” will read a series of characters until a white space is found
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can do fscanf(pRead, “%s%s”, name, hobby);
#include <stdio.h>
Main()
{
FILE *pRead;
char name[10];
pRead = fopen(“names.dat”, “r”);
if( pRead == NULL )
printf( “\nFile cannot be opened\n”);
else
printf(“\nContents of names.dat\n”);
fscanf( pRead, “%s”, name );
while( !feof(pRead) ) {
printf( “%s\n”, name );
fscanf( pRead, “%s”, name );
}
}
Kelly
11/12/86
Allen 04/05/77
Chelsea 03/30/90
6
49
12
Louisville
Atlanta
Charleston
Can you write a program that prints out the contents
of this information.dat file?
#include <stdio.h>
Main()
{
FILE *pRead;
char name[10];
char birthdate[9];
float number;
char hometown[20];
pRead = fopen(“information.dat”, “r”);
if( pRead == NULL )
printf( “\nFile cannot be opened\n”);
else
fscanf( pRead, “%s%s%f”, name, birthdate, &number, hometown );
while( !feof(pRead) ) {
printf( “%s \t %s \t %f \t %s\n”, name, birthdate, &number, hometown );
fscanf( pRead, “%s%s%f”, name, birthdate, &number, hometown );
}
}
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The fprintf() function sends information (the
arguments) according to the specified format to the
file indicated by stream. fprintf() works just like
printf() as far as the format goes.
#include <stdio.h>
Main()
{
FILE *pWrite;
char fName[20];
char lName [20];
float gpa;
pWrite = fopen(“students.dat”,”w”);
if( pWrite == NULL )
printf(“\nFile not opened\n”);
else
printf(“\nEnter first name, last name, and GPA separated”
printf(“Enter data separated by spaces:”);
scanf(“%s%s%f”, fName, lName, &gpa);
fprintf(pWrite, “%s \t %s \t % .2f \n”, fName, lName, gpa);
fclose(pWrite);
}
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Can you write a program that asks the user
for their
 Name
 Phone Number
 Bank account balance
And then prints this information to a data file
called accounts.dat ?
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Summary
 Include #include <iostream> directive at
beginning of program
 Use cin to take data from user
 Use cout to display data on screen
▪ Display multiple strings and integers in the same cout
statement by separating items with <<
#include <iostream>
#include<string>
using namespace std;
string name = “”;
int main(void)
{
cout<<“What is your name?”;
cin>>name;
cout<<endl<<“Hello”<<name.c_str();
return 0;
}
#include <iostream>
using namespace std;
int x = 25;
string str2 = “This is a test”;
int main( void )
{
cout<<“Test”<<1<<2<<“3”;
cout<<25 %7<<endl<<str2.c_str();
return 0;
}
Test 1234
This is a test
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How a computer stores data in its internal
memory
 RAM (Random-Access Memory) - temporary
 ROM (Read-Only Memory) – non volatile
 Store data in bytes
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How you store data temporarily
 Create variables based on fundamental types
(bool, char, int, float)
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constants: #define CONSTNAME value
sizeof()
TYPE
SIZE
VALUES
bool
1 byte
true (1) or false (0)
char
1 byte
‘a’ to‘z’ , ‘A’ to ‘Z’, ‘0’ to ‘9’, space, tab, and so on
int
4 bytes
-2,147,483,648 to 2,147,483,647
short
2 bytes
-32,768 to 32,767
long
4 bytes
-2,147,483,648 to 2,147,483,647
float
4 bytes
+ - (1.2 x 10^-38 to 3.4 x 10^38)
double
8 bytes
+- (2.3 x 10^-308 to -1.7 x 10^308)
What do each of the following evaluate to?
1. long elves = 8;
int dwarves = 8;
if(elves==dwarves) //true or false?
if(elves!=0) //true or false?
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2. int elves = 4;
int dwarves = 5;
if(dwarves > (2/3)) //true or false?
3. if(0 < x < 99) //true or false?
4. if(0<= (0<1))//true or false?
What do each of the following evaluate to?
1. long elves = 8;
int dwarves = 8;
if(elves==dwarves) //true
if(elves!=0) //true
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2. int elves = 4;
int dwarves = 5;
if(dwarves > (2/3)) //true
3. if(0 < x < 99) //true …TRUE (1) and FALSE (0) < 99
4. if(0<= (0<1))//true
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if(condition)
statement;
else if (condition)
statement;
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condition ? expr1 : expr2
 ex. z = ( x > y ) ? y : x ;
 cannot do
(x>y) ? count << “x is greater than y.” : cout << “x isn’t greater than y.”
switch(expression){
case expr1:
statement;
break;
case expr2:
statement;
break;
case expr3:
statement;
break;
default:
statements
break;
}
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while (condition)
{
statements;
}
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do
{
statements;
}
while(condition);
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for (initialization; condition; expression)
{
statements;
}
Incrementing: Prefix and Postfix
int x = 5;
int y = 6;
int z = y++
//z=6, y=7 postfix operator
int z = ++x
//z=6, x=6 prefix operator
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Keyword
Purpose
break
Exits the nearest enclosing “switch”
statement or iteration statement
continue
Starts the next loop of the nearest
enclosing iteration statement
goto
Jumps to a particular place in your code
return
Ends a function and returns a value
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Can you write a program that prints out the
following?
0123456789
for ( int count = 0; count < 10; count ++)
{
cout <<count<<“”;
}
1.
Write a conditional statement that will assign
x/y to x if y doesn’t equal 0.
2.
Write a while loop that calculates the
summative of positive integers from 1 to some
number n.
3.
Write a conditional statement that assigns x*y
if x is even; otherwise , if x is odd and y doesn’t
equal 0, assign x to x/y; if neither of the
preceding cases is true, output to the screen
that y is equal to 0.
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Function declaration
Function definition
Function call
#include <iostream>
using namespace std;
int add(int a, int b);
int main(void)
{
int number1, number2;
cout << “Enter the first value to be summed:”’
cin >> number1;
cout << “\nEnter the second:”;
}
cin >> number2;
cout << “\n The sum is: “ << add (number1, number2) <<endl;
int add(int a, int b)
{
return a+b;
}
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Write a function, called multiply that
multiplies two numbers and returns the result
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Declare classes
Create objects
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3 MAIN PRINCIPLES OF OOP
 Data abstraction – hiding data members and
implementation of a class behind an interface so that
the user of the class corrupt that data
 Encapsulation – each class represents a specific thing
or concept. Multiple classes combine to produce the
whole
 Polymorphism-objects can be used in more than one
program
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Classes are general models from which you
can create objects
Classes have data members either data types
or methods
Classes should contain a constructor method
and a destructor method
See handout for example of a program that
utilizes a class
class ClassName
{
memberList
};
memberList can be either data member
declarations or method declarations
Class Bow
{
//data member declarations
string color;
bool drawn;
int numOfArrows;
Bow(string aColor); //constructor
~Bow(); //destructor
};
//methods
void draw();
int fire();
Return_type
ClassName::methodName(argumentList)
{
methodImplementation
}
//draws the bow
Void Bow::draw()
{
drawn = true;
cout<< “The “<<color<<“bow has been drawn.”<<endl;
}
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Arrays
Pointers
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data_type array_name [number-of-elements];
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Two Dimensional Array
array_type array_name [number_ofelements1][number_of_elements2];
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type* pointer_name;
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ex.
int my_int;
int* my_int_pointer = &my_int;
Assigns the address of my_int to the pointer
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Copying strings from one to another
 char* strcpy(char* p, const char* q);
 char s[6];
strcpy(s, “Hello”);
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To combine strings
 char* strcat(char* p, const char* q);
 char s[12] = “Hello”
strcat(s, “World”);
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To copy n characters from q to the of p.
char* strncpy(char* p, const char* q, int n);
 char s [7] = “Say “;
char t[] = “Hi”;
strncpy (s, t, 2)
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Can you write a program using C++ that uses
a FOR loop to initialize a 2D array that looks
like the following {0,5,10,15}{0,2,4,6}
#include<iostream>
using namespace std;
int main(void)
{
int array[4][4];
for( int i = 0; i< 5; i++)
{
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Basic framework for a program
How to Comment
How to Print
How to store variables
How to Print stored variables
How to find the size of a variable
How to convert from one data type to
another
How to Declare Constants
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If statements
 Conventional
 Using conditional operator
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Switch-case statements
Loops
 While
 Do-While
 For
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Branching statements
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How to declare and implement functions
How to create arrays
How to create pointers
Useful string functions
Classes
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//this is how you comment
/*this is how
you comment */ Use for Multiple lines
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Used to create functions, classes, and variables
of the same name
Ex.
Namespace combat
{
void fire()
}
Namespace exploration
{
void fire()
}
To call a namespace
combat::fire()
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Say (to avoid having to put combat:: every
time
using namespace combat;
fire()
class aClass
{
public:
int anInt;
}
class aDerivedClass : public aClass
{
protected:
float aFloat;
};
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Used in place of a specific data type. For
example, use a template to add data types
together, whichever data type the user
wishes (i.e integers, floats)