CS102 Lesson2.pdf

CS 102 Computer Programming 1 Prepared by: Assoc. Prof. Michelle C. Decamora, MIT The Basics of a C++ Program ▸ Function: collection of statements; when executed, accomplishes something – May be predefined or user-defined ▸ Syntax: rules that specify which statements (instructions) a...

CS 102 Computer Programming 1 Prepared by: Assoc. Prof. Michelle C. Decamora, MIT The Basics of a C++ Program ▸ Function: collection of statements; when executed, accomplishes something – May be predefined or user-defined ▸ Syntax: rules that specify which statements (instructions) are legal ▸ Programming language: a set of rules, symbols, and special words ▸ Semantic rule: meaning of the instruction. Comments ▸ Comments are for the reader, not the compiler ▸ Two types: – Single line // This is a C++ program. It prints the sentence: // Welcome to C++ Programming. – Multiple line Special Symbols ▸ Special symbols ▸ Special symbols + ? - , = ;  Reserved Words (Keywords) ▸ Reserved words, keywords, or word symbols ▹ Are words that have special meaning and function in C++ programming. ▹ Include: ▹ int ▹ float ▹ double ▹ char ▹ const ▹ void ▹ return Identifiers ▸ Are names of things that appear in programs, such as variables, constants and functions. ▹ All identifiers must obey C++’s rules for identifiers. ▸ Consist of letters, digits, and the underscore character (_) ▹ No other symbols are permitted to form an identifier. ▸ Must begin with a letter or underscore. ▸ C++ is case sensitive ▹ NUMBER is not the same as number ▸ Two predefined identifiers are cin and cout ▸ Unlike reserved words, predefined identifiers may be redefined, but it is not a good idea. Identifiers (cont’d) ▸ Legal identifiers in C++: ▹ first ▹ conversion ▹ payRate Whitespaces ▸ Every C++ program contains whitespaces ▹ Include blanks, tabs, and newline characters ▸ Used to separate special symbols, reserved words, and identifiers ▸ Proper utilization of whitespaces is important ▹ Can be used to make the program readable Data Types ▸ Data type: set of values together with a set of operations ▸ C++ data types fall into three categories: 10 Simple Data Types ▸ Three categories of simple data: ▹ Integral: integers (numbers without a decimal) ▹ Floating-point: decimal numbers ▹ Enumeration type: user-defined data type 11 Simple Data Types (cont'd.) ▸ Integral data types are further classified into nine categories: ▹ char, short, int, long, bool ▹ unsigned char, unsigned short, unsigned int, unsigned long 12 Simple Data Types (cont'd.) ▸ Different compilers may allow different ranges of values. 13 int Data Type ▸ Examples: -6728 0 78 +763 ▸ Positive integers do not need a + sign ▸ No commas are used within an integer ▹ Commas are used for separating items in a list 14 bool Data Type ▸ bool type ▹ Two values: true and false ▹ Manipulate logical (Boolean) expressions ▸ true and false ▹ Logical values ▸ bool, true, and false ▹ Reserved words ▸ mon 15 char Data Type ▸ The smallest integral data type ▸ Used for characters: letters, digits, and special symbols ▸ Each character is enclosed in single quotes ▹ 'A', 'a', '0', '*', '+', '$', '&' ▸ A blank space is a character ▹ Written ' ', with a space left between the single quotes 16 Floating-Point Data Types ▸ C++ uses scientific notation to represent real numbers (floating-point notation) 17 Floating-Point Data Types (cont'd.) ▸ float: represents any real number ▹ Range: -3.4E+38 to 3.4E+38 (four bytes) ▸ double: represents any real number ▹ Range: -1.7E+308 to 1.7E+308 (eight bytes) Floating-Point Data Types (cont'd.) ▸ Maximum number of significant digits (decimal places) for float values is 6 or 7 ▸ Maximum number of significant digits for double is 15 ▸ Precision: maximum number of significant digits ▹ Float values are called single precision ▹ Double values are called double precision 19 Arithmetic Operators and Operator Precedence C++ arithmetic operators: – + addition – - subtraction – * multiplication – / division – % modulus operator +, -, *, and / can be used with integral and floating-point data types Operators can be unary or binary 20 Order of Precedence ▸ All operations inside of ( ) are evaluated first ▸ *, /, and % are at the same level of precedence and are evaluated next ▸ + and – have the same level of precedence and are evaluated last ▸ When operators are on the same level ▹ Performed from left to right (associativity) ▸ 3 * 7 - 6 + 2 * 5 / 4 + 6 means (((3 * 7) – 6) + ((2 * 5) / 4 )) + 6 21 Expressions ▸ If all operands are integers ▹ Expression is called an integral expression ▹ Yields an integral result ▹ Example: 2 + 3 * 5 ▸ If all operands are floating-point ▹ Expression is called a floating-point expression ▹ Yields a floating-point result ▹ Example: 12.8 * 17.5 - 34.50 22 Mixed Expressions ▸ Mixed expression: ▹ Has operands of different data types ▹ Contains integers and floating-point ▸ Examples of mixed expressions: 2 + 3.5 6 / 4 + 3.9 5.4 * 2 – 13.6 + 18 / 2 23 Mixed Expressions (cont'd.) ▸ Evaluation rules: ▹ If operator has same types of operands ▹ Evaluated according to the type of the operands ▹ If operator has both types of operands ▹ Integer is changed to floating-point ▹ Operator is evaluated ▹ Result is floating-point ▹ Entire expression is evaluated according to precedence rules 24 Type Conversion (Casting) ▸ Implicit type coercion: when value of one type is automatically changed to another type ▸ Cast operator : provides explicit type conversion static_cast(expression) Type Conversion (cont'd.) 26 string Type Programmer-defined type supplied in ANSI/ISO Standard C++ library Sequence of zero or more characters Enclosed in double quotation marks Null: a string with no characters Each character has relative position in string – Position of first character is 0 Length of a string is number of characters in it – Example: length of "William Jacob" is 13 27 Assignment Statement ▸ The assignment statement takes the form: ▸ Expression is evaluated and its value is assigned to the variable on the left side ▸ In C++, = is called the assignment operator Assignment Statement (cont'd.) 29 Saving and Using the Value of an Expression ▸ To save the value of an expression: ▹ Declare a variable of the appropriate data type ▹ Assign the value of the expression to the variable that was declared ▹ Use the assignment statement ▸ Wherever the value of the expression is needed, use the variable holding the value 30 Declaring & Initializing Variables ▸ Variables can be initialized when declared: int first=13, second=10; char ch=' '; double x=12.6; ▸ All variables must be initialized before they are used ▹ But not necessarily during declaration 31 Variable Initialization ▸ There are two ways to initialize a variable: int feet; ▹ By using the assignment statement feet = 35; ▹ By using a read statement cin >> feet; Thank you!