1、A First Book of ANSI CFourth Edition,Chapter 2 Getting Started in C Programming,A First Book of ANSI C, Fourth Edition,2,Objectives,Introduction to C Programming Programming Style Data Types Arithmetic Operations,A First Book of ANSI C, Fourth Edition,3,Objectives (continued),Variables and Declarati

2、ons Case Study: Temperature Conversion Common Programming and Compiler Errors,A First Book of ANSI C, Fourth Edition,4,Introduction to C Programming,A First Book of ANSI C, Fourth Edition,5,Introduction to C Programming (continued),C provides a comprehensive set of functions Stored in a set of files

3、 known as the standard library The standard library consists of 15 header files,A First Book of ANSI C, Fourth Edition,6,Introduction to C Programming (continued),A First Book of ANSI C, Fourth Edition,7,Introduction to C Programming (continued),A First Book of ANSI C, Fourth Edition,8,Identifiers,I

4、dentifiers in C consist of three types: Reserved words Standard identifiers Programmer-created identifiers,A First Book of ANSI C, Fourth Edition,9,Identifiers (continued),Reserved word: word that is predefined by the programming language for a special purpose and can only be used in a specified man

5、ner for its intended purpose Also referred to as keywords in C,A First Book of ANSI C, Fourth Edition,10,Identifiers (continued),A First Book of ANSI C, Fourth Edition,11,Identifiers (continued),Standard identifiers: words predefined in C Most of the standard identifiers are the names of functions t

6、hat are provided in the C standard library It is good programming practice to use standard identifiers only for their intended purpose,A First Book of ANSI C, Fourth Edition,12,Identifiers (continued),A First Book of ANSI C, Fourth Edition,13,Identifiers (continued),Programmer-created identifiers: s

7、elected by the programmer Also called programmer-created names Used for naming data and functions Must conform to Cs identifier rules Can be any combination of letters, digits, or underscores (_) subject to the following rules: First character must be a letter or underscore (_) Only letters, digits,

8、 or underscores may follow the initial character Blank spaces are not allowed Cannot be a reserved word,A First Book of ANSI C, Fourth Edition,14,Identifiers (continued),Examples of invalid C programmer-created names: 4ab7 calculate total while All uppercase letters used to indicate a constant A fun

9、ction name must be followed by parentheses An identifier should be descriptive: degToRadians() Bad identifier choices: easy, duh, justDoIt C is a case-sensitive language TOTAL, and total represent different identifiers,A First Book of ANSI C, Fourth Edition,15,The main() Function,A First Book of ANS

10、I C, Fourth Edition,16,The main() Function (continued),Function header line,Executable statements,A First Book of ANSI C, Fourth Edition,17,The printf() Function,printf() formats data and sends it to the standard system display device (i.e., the monitor) Inputting data or messages to a function is c

11、alled passing data to the function printf(Hello there world!); Syntax: set of rules for formulating statements that are “grammatically correct” for the language Messages are known as strings in C A string of characters is surrounded by double quotes printf(Hello there world!);,A First Book of ANSI C

12、, Fourth Edition,18,The printf() Function (continued),Function arguments,A First Book of ANSI C, Fourth Edition,19,The printf() Function (continued),Comment,Preprocessor command,Header file,Invoking or calling the printf() function,A First Book of ANSI C, Fourth Edition,20,The printf() Function (con

13、tinued),Output is: Computers, computers everywhere as far as I can C,Newline escape sequence,A First Book of ANSI C, Fourth Edition,21,Programming Style: Indentation,Except for strings, function names, and reserved words, C ignores all white space White space: any combination of one or more blank sp

14、aces, tabs, or new lines In standard form: A function name is placed, with the parentheses, on a line by itself starting at the left-hand corner The opening brace follows on the next line, under the first letter of the function name The closing function brace is placed by itself at the start of the

15、last line of the function,A First Book of ANSI C, Fourth Edition,22,Programming Style: Indentation (continued),Within the function itself, all program statements are indented two spaces Indentation is another sign of good programming practice, especially if the same indentation is used for similar g

16、roups of statements Dont do this: int main ( )printf (Hello there world! );return 0;,A First Book of ANSI C, Fourth Edition,23,Programming Style: Comments,Comments help clarify what a program does, what a group of statements is meant to accomplish, etc. The symbols /*, with no white space between th

17、em, designate the start of a comment; the symbols */ designate the end of a comment /* this is a comment */ Comments can be placed anywhere within a program and have no effect on program execution Under no circumstances may comments be nested /* this comment is /* always */ invalid */,A First Book o

18、f ANSI C, Fourth Edition,24,Programming Style: Comments (continued),A First Book of ANSI C, Fourth Edition,25,Data Types,Data type: set of values and a set of operations that can be applied to these values Built-in data type: is provided as an integral part of the language; also known as primitive t

19、ype,A First Book of ANSI C, Fourth Edition,26,Data Types (continued),A First Book of ANSI C, Fourth Edition,27,Data Types (continued),A literal is an acceptable value for a data type Also called a literal value or constant 2, 3.6, 8.2, and Hello World! are literal values because they literally displ

20、ay their values,A First Book of ANSI C, Fourth Edition,28,Data Types (continued),A First Book of ANSI C, Fourth Edition,29,Integer Data Types,A First Book of ANSI C, Fourth Edition,30,Integer Data Types (continued),int: whole numbers (integers) For example: 0, -10, 253, -26351 Not allowed: commas, d

21、ecimal points, special symbols char: stores individual characters (ASCII) For example: A, $, b, !,A First Book of ANSI C, Fourth Edition,31,Integer Data Types (continued),A First Book of ANSI C, Fourth Edition,32,Integer Data Types (continued),A First Book of ANSI C, Fourth Edition,33,Integer Data T

22、ypes (continued),A First Book of ANSI C, Fourth Edition,34,Floating-Point Data Types,A floating-point value (real number) can be the number zero or any positive or negative number that contains a decimal point For example: +10.625, 5., -6.2, 3251.92, +2 Not allowed: commas, decimal points, special s

23、ymbols float: single-precision number double: double-precision number Storage allocation for each data type depends on the compiler (use sizeof(),A First Book of ANSI C, Fourth Edition,35,Floating-Point Data Types (continued),float literal is indicated by appending an f or F long double is created b

24、y appending an l or L 9.234 indicates a double literal 9.234f indicates a float literal 9.234L indicates a long double literal,A First Book of ANSI C, Fourth Edition,36,Floating-Point Data Types (continued),A First Book of ANSI C, Fourth Edition,37,Exponential Notation,In numerical theory, the term

25、precision typically refers to numerical accuracy,A First Book of ANSI C, Fourth Edition,38,Exponential Notation (continued),A First Book of ANSI C, Fourth Edition,39,Arithmetic Operations,Arithmetic operators: operators used for arithmetic operations: Addition + Subtraction - Multiplication * Divisi

26、on / Modulus Division % Binary operators require two operands An operand can be either a literal value or an identifier that has a value associated with it,A First Book of ANSI C, Fourth Edition,40,Arithmetic Operations (continued),A simple binary arithmetic expression consists of a binary arithmeti

27、c operator connecting two literal values in the form: literalValue operator literalValue 3 + 7 12.62 - 9.8 .08 * 12.2 12.6 / 2. Spaces around arithmetic operators are inserted for clarity and can be omitted without affecting the value of the expression,A First Book of ANSI C, Fourth Edition,41,Displ

28、aying Numerical Values,Arguments are separated with commas printf(The total of 6 and 15 is %d, 6 + 15); First argument of printf() must be a string A string that includes a conversion control sequence, such as %d, is termed a control string Conversion control sequences are also called conversion spe

29、cifications and format specifiers printf() replaces a format specifier in its control string with the value of the next argument In this case, 21,A First Book of ANSI C, Fourth Edition,42,Displaying Numerical Values (continued),printf(The total of 6 and 15 is %d, 6 + 15); The total of 6 and 15 is 21

30、 printf (The sum of %f and %f is %f, 12.2, 15.754, 12.2 + 15.754); The sum of 12.200000 and 15.754000 is 27.954000,A First Book of ANSI C, Fourth Edition,43,Displaying Numerical Values (continued),A First Book of ANSI C, Fourth Edition,44,Displaying Numerical Values (continued),A First Book of ANSI

31、C, Fourth Edition,45,Displaying Numerical Values (continued),A First Book of ANSI C, Fourth Edition,46,Expression Types,Expression: any combination of operators and operands that can be evaluated to yield a value Integer expression: contains only integer operands; the result is an integer Floating-p

32、oint expression: contains only floating-point operands; the result is a double-precision In a mixed-mode expression the data type of each operation is determined by the following rules: If both operands are integers, result is an integer If one operand is real, result is double-precision,A First Boo

33、k of ANSI C, Fourth Edition,47,Integer Division,15/2 = 7 Integers cannot contain a fractional part Remainder is truncated % is the modulus or remainder operator 9 % 4 is 1 17 % 3 is 2 14 % 2 is 0,A First Book of ANSI C, Fourth Edition,48,Negation,A unary operator is one that operates on a single ope

34、rand, e.g., negation (-) The minus sign in front of a single numerical value negates (reverses the sign of) the number,A First Book of ANSI C, Fourth Edition,49,Negation (continued),A First Book of ANSI C, Fourth Edition,50,Operator Precedence and Associativity,Two binary arithmetic operator symbols

35、 must never be placed side by side Parentheses may be used to form groupings Expressions in parentheses are evaluated first Parentheses may be enclosed by other parentheses Parentheses cannot be used to indicate multiplication,A First Book of ANSI C, Fourth Edition,51,Operator Precedence and Associa

36、tivity (continued),Three levels of precedence: All negations are done first Multiplication, division, and modulus operations are computed next; expressions containing more than one of these operators are evaluated from left to right as each operator is encountered Addition and subtraction are comput

37、ed last; expressions containing more than one addition or subtraction are evaluated from left to right as each operator is encountered,A First Book of ANSI C, Fourth Edition,52,Operator Precedence and Associativity (continued),Example: 8 + 5 * 7 % 2 * 4 = 8 + 35 % 2 * 4 = 8 + 1 * 4 = 8 + 4 = 12,A Fi

38、rst Book of ANSI C, Fourth Edition,53,Operator Precedence and Associativity (continued),A First Book of ANSI C, Fourth Edition,54,Variables and Declarations,Variables are names given by programmers to computer storage Variable name usually limited to 255 characters Variable names are case sensitive,

39、A First Book of ANSI C, Fourth Edition,55,Variables and Declarations (continued),A First Book of ANSI C, Fourth Edition,56,Variables and Declarations (continued),num1 = 45; num2 = 12; total = num1 + num2;,Assignment statements,A First Book of ANSI C, Fourth Edition,57,Variables and Declarations (con

40、tinued),A First Book of ANSI C, Fourth Edition,58,Declaration Statements,Naming and specifying the data type that can be stored in each variable is accomplished using declaration statements Declaration statements within a function appear immediately after the opening brace of a function function nam

41、e() declaration statements; other statements; Definition statements define or tell the compiler how much memory is needed for data storage,A First Book of ANSI C, Fourth Edition,59,Declaration Statements (continued),A First Book of ANSI C, Fourth Edition,60,Declaration Statements (continued),A First

42、 Book of ANSI C, Fourth Edition,61,Declaration Statements (continued),A First Book of ANSI C, Fourth Edition,62,Declaration Statements (continued),A First Book of ANSI C, Fourth Edition,63,Declaration Statements (continued),You can omit the f and let the compiler convert the double precision value i

43、nto a float value when the assignment is made,A First Book of ANSI C, Fourth Edition,64,Selecting Variable Names,Make variable names descriptive Limit variable names to approximately 20 characters Start the variable name with a letter, rather than an underscore (_) In a variable name consisting of s

44、everal words, capitalize the first letter of each word after the first,A First Book of ANSI C, Fourth Edition,65,Selecting Variable Names (continued),Use variable names that indicate what the variable corresponds to, rather than how it is computed Add qualifiers, such as Avg, Min, Max, and Sum to co

45、mplete a variables name where appropriate Use single-letter variable names, such as i, j, and k, for loop indexes,A First Book of ANSI C, Fourth Edition,66,Initialization,Declaration statements can be used to store an initial value into declared variables int numOne = 15; When a declaration statemen

46、t provides an initial value, the variable is said to be initialized Literals, expressions using only literals such as 87.0 + 12 2, and expressions using literals and previously initialized variables can all be used as initializers within a declaration statement,A First Book of ANSI C, Fourth Edition

47、,67,Case Study: Temperature Conversion,A friend of yours is going to Spain, where temperatures are reported using the Celsius temperature scale. She has asked you to provide her with a list of temperatures in degrees Fahrenheit, and the equivalent temperature in degrees Celsius. The formula relating

48、 the two temperatures is Celsius = 5/9(Fahrenheit 32). Initially, you are to write and test a program that correctly converts the Fahrenheit temperature of 75 degrees into its Celsius equivalent.,A First Book of ANSI C, Fourth Edition,68,Case Study: Temperature Conversion (continued),A First Book of

49、 ANSI C, Fourth Edition,69,Common Programming Errors,Omitting the parentheses, (), after main Omitting or incorrectly typing the opening brace, , that signifies the start of a function body Omitting or incorrectly typing the closing brace, , that signifies the end of a function Misspelling the name

50、of a function; for example, typing print() instead of printf() Forgetting to close a string passed to printf() with a double quote symbol,A First Book of ANSI C, Fourth Edition,70,Common Programming Errors (continued),Omitting the semicolon at the end of each executable statement Forgetting to inclu

51、de n to indicate a new line Forgetting to declare all the variables used in a program Storing an incorrect data type in a declared variable Using a variable in an expression before a value has been assigned to the variable,A First Book of ANSI C, Fourth Edition,71,Common Programming Errors (continued),Dividing integer values incorrectly Mixing data