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Do you know the syntax for each of these, used to read and write to data files?  Pointers: think of it as the memory address of the file  fopen() 

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Presentation on theme: "Do you know the syntax for each of these, used to read and write to data files?  Pointers: think of it as the memory address of the file  fopen() "— Presentation transcript:

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2 Do you know the syntax for each of these, used to read and write to data files?  Pointers: think of it as the memory address of the file  fopen()  fclose()  fscanf()  fprintf()

3  fopen() returns a FILE pointer back to the pRead variable #include Main() { FILE *pRead; pRead = fopen(“file1.dat”, “r”); if(pRead == NULL) printf(“\nFile cannot be opened\n”); else printf(“\nFile opened for reading\n”); }

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5  Pretty basic.

6  Reads a single field from a data file  “%s” will read a series of characters until a white space is found  can do fscanf(pRead, “%s%s”, name, hobby);

7 #include 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 ); }

8 Kelly11/12/866Louisville Allen04/05/7749Atlanta Chelsea03/30/9012Charleston Can you write a program that prints out the contents of this information.dat file?

9 #include 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 ); }

10  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. printf()

11 #include 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); }

12  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 ?

13  Summary  Include #include 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 <<

14 #include using namespace std; string name = “”; int main(void) { cout<<“What is your name?”; cin>>name; cout<<endl<<“Hello”<<name.c_str(); return 0; }

15 #include 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; }

16 Test 1234 This is a test

17  How a computer stores data in its internal memory  RAM (Random-Access Memory) - temporary  ROM (Read-Only Memory) – non volatile  Store data in bytes  How you store data temporarily  Create variables based on fundamental types (bool, char, int, float)  constants: #define CONSTNAME value  sizeof()

18 TYPESIZEVALUES bool1 bytetrue (1) or false (0) char1 byte‘a’ to‘z’, ‘A’ to ‘Z’, ‘0’ to ‘9’, space, tab, and so on int4 bytes-2,147,483,648 to 2,147,483,647 short2 bytes-32,768 to 32,767 long4 bytes-2,147,483,648 to 2,147,483,647 float4 bytes+ - (1.2 x 10^-38 to 3.4 x 10^38) double8 bytes+- (2.3 x 10^-308 to -1.7 x 10^308)

19  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? 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?

20  What do each of the following evaluate to? 1. long elves = 8; int dwarves = 8; if(elves==dwarves) //true if(elves!=0) //true 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

21  if(condition) statement; else if (condition) statement;  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.”

22 switch(expression){ case expr1: statement; break; case expr2: statement; break; case expr3: statement; break; default: statements break; }

23  while (condition) { statements; }  do { statements; } while(condition);

24  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

25 KeywordPurpose breakExits the nearest enclosing “switch” statement or iteration statement continueStarts the next loop of the nearest enclosing iteration statement gotoJumps to a particular place in your code returnEnds a function and returns a value

26  Can you write a program that prints out the following? 0 1 2 3 4 5 6 7 8 9

27 for ( int count = 0; count < 10; count ++) { cout <<count<<“”; }

28 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.

29  Function declaration  Function definition  Function call

30 #include 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; }

31  Write a function, called multiply that multiplies two numbers and returns the result

32  Declare classes  Create objects  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

33  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

34 class ClassName { memberList }; memberList can be either data member declarations or method declarations

35 Class Bow { //data member declarations string color; bool drawn; int numOfArrows; Bow(string aColor); //constructor ~Bow(); //destructor //methods void draw(); int fire(); };

36 Return_type ClassName::methodName(argumentList) { methodImplementation }

37 //draws the bow Void Bow::draw() { drawn = true; cout<< “The “<<color<<“bow has been drawn.”<<endl; }

38  Arrays  Pointers

39  data_type array_name [number-of-elements];  Two Dimensional Array array_type array_name [number_ofelements1][number_of_elements2];

40  type* pointer_name;  ex. int my_int; int* my_int_pointer = &my_int; Assigns the address of my_int to the pointer

41  Copying strings from one to another  char* strcpy(char* p, const char* q);  char s[6]; strcpy(s, “Hello”);  To combine strings  char* strcat(char* p, const char* q);  char s[12] = “Hello” strcat(s, “World”);

42  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)

43  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}

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45 #include using namespace std; int main(void) { int array[4][4]; for( int i = 0; i< 5; i++) {

46  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

47  If statements  Conventional  Using conditional operator  Switch-case statements  Loops  While  Do-While  For  Branching statements

48  How to declare and implement functions  How to create arrays  How to create pointers  Useful string functions  Classes

49  //this is how you comment  /*this is how you comment */ Use for Multiple lines

50  Used to create functions, classes, and variables of the same name  Ex. Namespace combat { void fire() } Namespace exploration { void fire() }

51  To call a namespace combat::fire()  Say (to avoid having to put combat:: every time using namespace combat; fire()

52 class aClass { public: int anInt; } class aDerivedClass : public aClass { protected: float aFloat; };

53  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)


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