02a fundamental c++ types, arithmetic
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The document discusses fundamental C++ types including integers, characters, and floating-point numbers. It describes integer types like int, short, and long and their typical sizes. Character types represent single characters with examples of escape codes. Floating-point types can represent real numbers in formats like float and double. The document also covers C++ concepts such as variable definitions and declarations, arithmetic operators, assignment, and increment/decrement operators.
02a fundamental c++ types, arithmetic
- 2. 2 C++ has a large number of fundamental or built-in types The fundamental types fall into one of three categories Integer Floating-point Character Integer type The basic integer type is int The size of an int depends on the machine and the compiler On PCs it is normally 16 or 32 bits Other integers types short: typically uses less bits (often 2 bytes) long: typically uses more bits (often 4 bytes) Different types allow programmers to use resources more efficiently Standard arithmetic and relational operations are available for these types Fundamental C++ Types
- 3. 3 Integer constants Integer constants are positive or negative whole numbers Integer constant forms Decimal Digits 0, 1, 2, 3, 4, 5, 6, 7 Octal (base 8) Digits 0, 1, 2, 3, 4, 5, 6, 7 Hexadecimal (base 16) Digits 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, a , b, c, d, e, f, A, B, C, D, E, F Consider 31 oct and 25 dec Decimal Constants Examples 97 40000 50000 23a (illegal) The type of the constant depends on its size, unless the type is specified
- 4. 4 Character type Char is for specifying character data char variable may hold only a single lowercase letter, a single upper case letter, a single digit, or a single special character like a $, 7, *, etc. case sensitive, i.e. a and A are not same. ASCII is the dominant encoding scheme Examples ' ' encoded as 32 '+' encoded as 43 'A' encoded as 65 'Z' encoded as 90 'a' encoded as 97 'z' encoded as 122
- 5. 5 Character type Explicit (literal) characters within single quotes 'a','D','*‘ Special characters - delineated by a backslash Two character sequences (escape codes) Some important special escape codes t denotes a tab n denotes a new line denotes a backslash ' denotes a single quote " denotes a double quote 't' is the explicit tab character, 'n' is the explicit new line character, and so on
- 6. 6 Floating-point type Floating-point type represent real numbers Integer part Fractional part The number 108.1517 breaks down into the following parts 108 - integer part 1517 - fractional part C++ provides three floating-point types Float (often 4 bytes) Declares floating point numbers with up to 7 significant digits Double long double (often 10 bytes) Declares floating point numbers with up to 19 significant digits.
- 7. 7 Memory Concepts Variable Variables are names of memory locations Correspond to actual locations in computer's memory Every variable has name, type, size and value When new value placed into variable, overwrites previous value Reading variables from memory is nondestructive cin >> integer1; Assume user entered 45 cin >> integer2; Assume user entered 72 sum = integer1 + integer2; integer1 45 integer2 72 integer1 45 sum 117 integer2 72 integer1 45
- 8. 8 Names (naming entities) Used to denote program values or components A valid name is a sequence of Letters (upper and lowercase) A name cannot start with a digit Names are case sensitive MyObject is a different name than MYOBJECT There are two kinds of names Keywords Identifiers
- 9. 9 Keywords Keywords are words reserved as part of the language int, return, float, double They cannot be used by the programmer to name things They consist of lowercase letters only They have special meaning to the compiler
- 10. 10 C++ key words C++ Keywords Keywords common to the C and C++ programming languages auto break case char const continue default do double else enum extern float for goto if int long register return short signed sizeof static struct switch typedef union unsigned void volatile while C++ only keywords asm bool catch class const_cast delete dynamic_cast explicit false friend inline mutable namespace new operator private protected public reinterpret_cast static_cast template this throw true try typeid typename using virtual wchar_t
- 11. 11 Identifiers Identifiers are used to name entities in c++ It consists of letters, digits or underscore Starts with a letter or underscore Can not start with a digit Identifiers should be Short enough to be reasonable to type Standard abbreviations are fine (but only standard abbreviations) Long enough to be understandable When using multiple word identifiers capitalize the first letter of each word Examples Grade Temperature CameraAngle IntegerValue
- 12. 12 Definitions/declaration All objects (or variable) that are used in a program must be defined (declared) An object definition specifies Type Identifier General definition form Type Id, Id, ..., Id; Known type List of one or more identifiers (Value of an object is whatever is in its assigned memory location) Examples Char Response; int MinElement; float Score; float Temperature; int i; int n; char c; float x; Location in memory where a value can be stored for program use
- 13. 13 Type compatibilities Rule is to store the values in variables of the same type This is a type mismatch: int int_variable; int_variable = 2.99; If your compiler allows this, int variable will most likely contain the value 2, not 2.99
- 14. 14 Stream extraction and assignment operator >> (stream extraction operator) When used with cin, waits for the user to input a value and stores the value in the variable to the right of the operator The user types a value, then presses the Enter (Return) key to send the data to the computer Example: int myVariable; cin >> myVariable; Waits for user input, then stores input in myVariable = (assignment operator) Assigns value to a variable Binary operator (has two operands) Example: sum = variable1 + variable2;
- 15. 15 A simple program to add two numbers 1 //example 2 // program to add two numbers 3 #include <iostream.h> 4 5 int main() 6 { 7 int integer1, integer2, sum; // declaration 8 9 cout << "Enter first integern"; // prompt 10 cin >> integer1; // read an integer 11 cout << "Enter second integern"; // prompt 12 cin >> integer2; // read an integer 13 sum = integer1 + integer2; // assignment of sum 14 cout << "Sum is " << sum << endl; // print sum 15 16 return 0; // indicate that program ended successfully 17 } •Notice how cin is used to get user input. General form is cin>>identifier; •Cin is an I stream object •streams input from standard input •uses the >> (input operator) •Note that data entered from the keyboard must be compatible with the data type of the variable endl flushes the buffer and prints a newline. •Variables can be output using cout << variableName. •Generl form is cout<<expression; •An expression is any c++ expression(string constant, identifier, formula or function call) •Cout is an o stream object •streams output to standard output •uses the << (output) operator Calculations can be performed in output statements: alternative for lines 13 and 14: cout << "Sum is " << integer1 + integer2 << std::endl; Use stream extraction operator with standard input stream to obtain user input. Concatenating, chaining or cascading stream insertion operations.
- 17. 17 program to find the area of rectangle Tells the compiler to use names in iostream in a “standard” way
- 18. 18 output
- 19. 19 Program to find total number of students in all sections 1. //example 2. //to find the total number of students in all sections. 3. # include <iostream> //preprocessor directive 4. int main() 5. { 6. int number_of_sections, students_per_section; //declaration 7. int total_students; 8. cout<<"enter the number of sectionsn"; //prompt to enter total number of sections 9. cin>>number_of_sections; //reading number of sections 10. cout<<"enter the number of students per sectionn"; //prompt to enter number 11. // of students per section 12. cin>>students_per_section; //reading students per section 13. 14. total_students = number_of_sections * students_per_section; //assignment to total students 15. cout<<"total number of students in all the sections isn"; //prompt 16. cout<<total_students; // show the number of total students 17. return 0; 18. }
- 20. 20 output
- 21. 21 Arithmetic Arithmetic is performed with operators. Arithmetic operators are listed in following table Modulus operator returns the remainder of integer division 7 % 5 evaluates to 2 Integer division truncates remainder 7 / 5 evaluates to 1 C++ operation Arithmetic operator Algebraic expression C++ expression Addition + f + 7 f + 7 Subtraction - p – c p - c Multiplication * bm b * m Division / x / y x / y Modulus % r mod s r % s
- 22. 22 Results of Arithmetic operators Arithmetic operators can be used with any numeric type. An operand is a number or variable used by the operator e.g. integer1 + integer2 + is operator integer1 and integer2 are operands Result of an operator depends on the types of operands If both operands are int, the result is int If one or both operands are double, the result is double
- 23. 23
- 24. 24 Examples comparing mathematical and C++ expressions
- 25. 25 Operator precedence Some arithmetic operators act before others (e.g., multiplication before addition) Be sure to use parenthesis when needed Example: Find the average of three variables a, b and c Do not use: a + b + c / 3 (incorrect) Use: (a + b + c ) / 3 (correct)
- 26. 26 Rules of operator precedence Operator(s) Operation(s) Order of evaluation (precedence) () Parentheses Evaluated first. If the parentheses are nested, the expression in the innermost pair is evaluated first. If there are several pairs of parentheses “on the same level” (i.e., not nested), they are evaluated left to right. *, /, or % Multiplication Division Modulus Evaluated second. If there are several, they are evaluated left to right. + or - Addition Subtraction Evaluated last. If there are several, they are evaluated left to right.
- 27. 27 Operator Precedence An example to understand operator precedence. 20 - 4 / 5 * 2 + 3 * 5 % 4 (4 / 5) ((4 / 5) * 2) ((4 / 5) * 2) (3 * 5) ((4 / 5) * 2) ((3 * 5) % 4) (20 -((4 / 5) * 2)) ((3 * 5) % 4) (20 -((4 / 5) * 2)) + ((3 * 5) % 4)
- 28. 28 Assignment operators = is the assignment operator Used to assign a value to a variable An assignment statement changes the value of a variable General Form: identifier = expression; The single variable to be changed is always on the left of the assignment operator ‘=‘ On the right of the assignment operator can be Constants For example age = 21; Variables For example my_cost = your_cost; Expressions For example circumference = diameter * 3.14159;
- 29. 29 Assignment operators The ‘=‘ operator in C++ is not an equal sign The following statement cannot be necessarily true in algebra number_of_bars = number_of_bars + 3; In C++ it means the new value of number_of_bars is the previous value of number_of_bars plus 3
- 30. 30 Assignment expression abbreviations Program can be written and compiled a bit faster by the use of abbreviated assignment operators C++ provides several assignment operators for abbreviating assignment expressions. Addition assignment operator c = c + 3; abbreviated to c += 3; Statements of the form variable = variable operator expression; can be rewritten as variable operator= expression; Other assignment operators d -= 4 (d = d - 4) e *= 5 (e = e * 5) f /= 3 (f = f / 3) g %= 9 (g = g % 9)
- 31. 31 Arithmetic assignment operators Assignment operator Sample expression Explanation Assigns Assume: int c = 3, d = 5, e = 4, f = 6, g = 12; += c += 7 c = c + 7 10 to c -= d -= 4 d = d - 4 1 to d *= e *= 5 e = e * 5 20 to e /= f /= 3 f = f / 3 2 to f %= g %= 9 g = g % 9 3 to g
- 32. 32 Increment and Decrement Operators Increment and decrement operators are unary operators as they require only one operand. ++ unary increment operator Adds 1 to the value of a variable x ++; is equivalent to x = x + 1; Pre-increment When the operator is used before the variable (++c) Variable is changed, then the expression it is in is evaluated Post-increment When the operator is used after the variable (c++) Expression the variable is in executes, then the variable is changed.
- 33. 33 Increment and Decrement Operators -- -- unary decrement operator Subtracts 1 from the value of a variable x --; is equivalent to x = x – 1; Pre-decrement When the operator is used before the variable (--c) Variable is changed, then the expression it is in is evaluated. Post-decrement When the operator is used after the variable (c--) Expression the variable is in executes, then the variable is changed.
- 34. 34 Increment and Decrement Operators Example If c = 5, then cout << ++c; c is changed to 6, then printed out cout << c++; Prints out 5 (cout is executed before the increment) c then becomes 6 When variable not in expression Preincrementing and postincrementing have same effect ++c; cout << c; and c++; cout << c; are the same
- 35. 35 Summarizing increment and decrement operators in a table Operator Called Sample expression Explanation ++ preincrement ++a Increment a by 1, then use the new value of a in the expression in which a resides. ++ postincrement a++ Use the current value of a in the expression in which a resides, then increment a by 1. -- predecrement --b Decrement b by 1, then use the new value of b in the expression in which b resides. -- postdecrement b-- Use the current value of b in the expression in which b resides, then decrement b by 1. The associativity of these unary operators is from right to left
- 36. 36 An example to understand the effect of pre- increment and post-increment 1 // example 2 // Pre incrementing and post incrementing. 3 #include <iostream.h> 4 5 8 // function main begins program execution 9 int main() 10 { 11 int c; // declare variable 12 13 // demonstrate pos tincrement 14 c = 5; // assign 5 to c 15 cout << c << endl; // print 5 16 cout << c++ << endl; // print 5 then post increment 17 cout << c << endl << endl; // print 6 18 19 // demonstrate pre increment 20 c = 5; // assign 5 to c 21 cout << c << endl; // print 5 22 cout << ++c << endl; // pre increment then print 6 cout << c << endl; // print 6 24 25 return 0; // indicate successful termination 26 27 } // end function main
- 37. 37 output Cout<<c prints c =5 Cout<<c++ prints c =5 then increment c by 1 to 6 Cout<<c prints c =6 Cout<<c prints c =5 Cout<<++c first increment c by one to to 6 then prints c =6 Cout<<c prints c =6
- 38. 38 Precedence of the operators encountered so far Operators Associativity Type () left to right parentheses ++ -- static_cast<type>() left to right unary (postfix) ++ -- + - right to left unary (prefix) * / % left to right multiplicative + - left to right additive << >> left to right insertion/extraction < <= > >= left to right relational == != left to right equality ?: right to left conditional = += -= *= /= %= right to left assignment , left to right comma