Bài giảng Introduction to Computer Programming (C language) - Chapter 2: C Program Structure and its Components - Võ Thị Ngọc Châu

 2012. 
 [2] “The C Programming Language”, 2nd Ed. 
 – Brian W. Kernighan and Dennis M. Ritchie, 
 Prentice Hall, 1988 
 and others, especially those on the Internet 
 3 
Content 
 Introduction 
 A Sample C Program 
 Coding Styles 
 Data and Standard Output Function 
 Data and Standard Input Function 
 Data Processing: Simple Example 
 Summary 
 4 
 Introduction 
 ―In our experience, C has proven to be a 
 pleasant, expressive, and versatile 
 language for a wide variety of programs. It 
 is easy to learn, and it wears well as one’s 
 experience with it grows.‖ 
  [2], Brian W. Kernighan and Dennis M. Ritchie 
versatile = able to be used for many different purposes 5 
Introduction 
Design of Library Library 
 program (Header: *.h) (Object code: *.lib; *.dll; *.so) 
 Editor Preprocessor Compiler Linker Executable 
 Program 
 Source code Enhanced source code Object code 
 *.h + *.c *.h + *.c (*.cpp) *.obj 
 (*.cpp) 
 gcc; g++ 
 Integrated Development Environment (IDE): 
 Visual Studio; Eclipse; Qt Creator; Code block; Online tool; etc 
 Programming tasks using the C language 6 
Introduction 
Design of Library Library 
 program (Header: *.h) (Object code: *.lib; *.dll; *.so) 
 Editor Preprocessor Compiler Linker Executable 
 Program 
 Source code Enhanced source code Object code 
 *.h + *.c *.h + *.c (*.cpp) *.obj 
 (*.cpp) 
 gcc; g++ 
 Integrated Development Environment (IDE): 
 Visual Studio; Eclipse; Qt Creator; Code block; Online tool; etc 
 Programming tasks using the C language 7 
A Sample C Program 
 A source code file named C2_example1.c 
 Purpose: display our university’s name 
 and course’s name on the screen 8 
A Sample C Program 
 A source code file named C2_example1.c 
 Purpose: display our university’s name 
 and course’s name on the screen 9 
 A Sample C Program 
 Every C program requires the specific 
 function named ―main‖ exactly. 
 The body of the 
 ―main‖ function is 
 enclosed in the 
 brackets {}. 
The body of the The specific 
―main‖ function is A source code file named C2_example1.c extension of 
made to serve the C source 
specific purpose. Purpose: display our university’s name code files 
 and course’s name on the screen 10 
A Sample C Program 
 A directive to the C preprocessor before the program is compiled. 
 is used for standard input/output library functions such 
 as the output function printf() and the input function scanf(). 
 This global definition section is 
 used for external headers. 
 Comments in /**/ or after // 
 A source code file named C2_example1.c 
 Purpose: display our university’s name 
 and course’s name on the screen 11 
 A Sample C Program 
 File name: following the naming conventions 
 supported by the OS with the .c extension 
  Not include some special symbols: *, /, \,  
  Avoid using special symbols even if they are allowed 
  Prefer descriptive names 
 The ―main‖ function 
  All the files and libraries are compiled into a single 
 executable program file with exactly one ―main‖ 
 function. 
  The starting point for the execution of a C program 
  Note: The C language is case-sensitive. 
 MAIN vs. Main vs. main 
 12 
A Sample C Program 
 The ―main‖ function 
 void main(){ Open bracket ―{― to start the body section 
 } Corresponding close bracket ―}― to end the body 
 section 
 int main(void){ 
 } Place for specifying the parameters of the function 
 Empty or void: no parameter is specified 
 Data type of the value returned by the ―main‖ function 
 int: a status value: 0 = no error; 1 = error 
 EXIT_SUCCESS = 0; EXIT_FAILURE = 1 
 void: no value is returned 13 
 A Sample C Program 
 The ―main‖ function 
 void main(){ 
 printf("Ho Chi Minh City University of Technology\n"); statement 
 printf("Introduction to Computer Programming\n"); statement 
 } 
Each statement 
 - ended with a semicolon (;) 
 - stretched on multiple lines with a backslash \ at the end 
 - able to be grouped in the brackets {} 
 - not consider spaces 
Several statement types 
 - sequence: function calling, assignment, break, continue, return,  
 - selection: if, if else, switch 
 - repetition: for, while, do while 14 
 A Sample C Program 
 In addition to ―main‖, there are keywords/reserved words 
 in the C language. 
 [1], p. 42 
 15 
 A Sample C Program 
 The global definition section 
  Lines beginning with # 
 The #include directive tells the preprocessor to include 
 the contents of another file. 
 . #include ―myHeader.h‖ 
 . A personal header file in the current directory 
 . #include 
 . A standard library file in the standard directory \include 
 The #define directive to set up symbolic replacements 
 The #if test at compile-time to look at the symbols in 
 #define and turn on and off which lines the compiler uses 
  Function prototypes to validate function calls 
  Global variable declarations 
 16 
 A Sample C Program 
 Comments 
  /**/: multi-line comment 
  //: single-line comment 
 17 
 A Sample C Program 
How to get the program run for the specified purpose? *.c => a machine code file (e.g. *.exe) 
 A source code file named C2_example1.c 
 Purpose: display our university’s name 
 and course’s name on the screen 18 
 A Sample C Program 
 Edit: 
 C2_example1.c 
 Compile: 
 gcc –Wall C2_example1.c –o C2_example1 
 -Wall: display all the warning types along with the errors if any 
 -o C2_example1: specify a name for the resulting executable 
 program 
 Run: 
 C2_example1 
 19 
 A Sample C Program 
 GCC = GNU Compiler Collection 
 The free GNU C++: gcc.gnu.org/install/ 
 binaries.html 
 GCC is available for most platforms, 
 including Linux, Mac OS X (via Xcode) and 
 Windows—via tools like Cygwin 
 (www.cygwin.com) and MinGW 
 (www.mingw.org) 
 Free IDEs: Micrsoft Visual Studio Express 
 Editions, CodeBlock, Dev C++,  
 20 
Coding Styles 
 Which 
 (A) 
 one do 
 you 
 prefer? 
 (B) 
 (C) 21 
Coding Styles 
 The three different formatted examples for 
 the same purpose return the same result: 
 What problems might we face with (A)? 
 What problems might we face with (B)? 
 What problems might we face with (C)? 
 What else if the program is not defined with 
 just a few lines; instead, with thousands of 
 lines? 
 22 
 Coding Styles 
 Alignment 
  Statements are aligned level by level based on 
 the block {} that they are contained. 
 Separation (White space) 
  Each statement should placed on a single line. 
  Blank lines should be used for more clarity. 
 Comment 
  A comment is added at any level for 
 explanation, marking, tracking,  
  Comments from the pseudo code helpful for 
 program development 
  Never abuse comments to make a program clear 
 23 
Coding Styles 
 Naming conventions 
  Descriptive 
  Classified 
  Consistent 
  Agreements if any 
 Easy to remember, easy to be referred, easy to 
 be communicated 
 Less error-prone 
 24 
 Coding Styles 
 Naming conventions 
  What can you name in a C program except file 
 names? 
 Function: your defined modular processing unit 
 Variable: a location in memory where a value can be 
 stored for use by a program 
 Symbolic constant: constant represented as a symbol (a 
 string) that will be replaced with the value it stands for 
 A name should reflect the content and role of the 
 thing you define in a C program. 25 
Coding Styles 
 Naming conventions 
  Create a name made up of at most 31 letters, 
 digits, underscore ―_‖ and starting with a letter 
  Consider verbs, nouns, phrases,  
  Consider a length of each name: short/long 
  Consider lower-case/upper-case letters 
  Consider prefix/suffix parts 
 Function: verb, phrase 
 Variable: noun, lower-case letters, short for loops 
 . Global variable: prefix g_ 
 . Data type: suffix _ptr for pointers 
 Symbolic constant: upper-case letters, underscores 26 
 Coding Styles 
Should  Should not X 
 check_for_errors() error_checking() 
 dump_data_to_file() 
 is_any_upper_case() any_upper_case_test() 
 get_an_upper_case() return_an_upper_case() 
 set_first_upper_case() change_first_upper_case() 
 Student *student_prt; Student * student; 
 int g_thread_number; int thread_number; 
 static const double PI static const double Pi = 
 = 3.14; 3.14; 
 #define SIZE 10 #define size 10 
   27 
 Coding Styles 
 How to make the following program clearer? 
 28 
 Coding Styles 
 How to make the following program clearer? 
 29 
Coding Styles 
 Check your naming conventions in your 
 pseudo code 
 How many names would you like to 
 rename? 
 What else have you changed on your 
 pseudo code? 
 How clearer is your pseudo code? 
 30 
 Coding Styles 
 Practice the formatting rules and conventions 
 to be part of your own coding habit 
 Make sure that your submitted programs are 
 always well-formatted 
 Make sure that your future programs are 
 readable, interpretable, able to be maintained, 
 reused, and extended 
 More information about coding styles at: 
   
   
 31 
 Data and Standard Output 
 Function 
 Standard output function: printf() 
  #include 
  Output the data to the standard output stream 
 A sequence of bytes flows from main memory to an 
 output device: display screen, printer, disk drive, 
 network connection, and so on. 
 Normally and automatically, the standard output 
 stream is connected to the screen. 
Examples: 
 32 
 Data and Standard Output 
 Function 
 Formatting capabilities of the printf function 
  Rounding floating-point values to an indicated number 
 of decimal places. 
  Aligning a column of numbers with decimal points 
 appearing one above the other. 
  Right justification and left justification of outputs. 
  Inserting literal characters at precise locations in a 
 line of output. 
  Representing floating-point numbers in exponential 
 format. 
  Representing unsigned integers in octal and 
 hexadecimal format. 
  Displaying all types of data with fixed-size field widths 
 and precisions. 33 
 Data and Standard Output 
 Function 
 - format-control-string describes the output format. 
 - other-arguments (optional) correspond to each conversion 
 specification in format-control-string. 
 Each conversion specification begins with a percent sign (%) and 
 ends with a conversion specifier. 
 There can be many conversion specifications in one format control 
 string. 
Examples: 
The 1st conversion specification: %5.2f => argument: x 
 nd
The 2 conversion specification: %5.2f => argument: y 34 
 Data and Standard Output 
 Function 
format-control-string is summarized as follows: 
 %[flag][width][.precision]specifier 
specifier = d/i, u, o, x/X, f/F, e/E, g/G, a/A, c, s, p, n, % 
precision = .number, .* 
width = number, * 
flag = +, -, space, #, 0 
 35 
Data and Standard Output 
Function 
 36 
Data and Standard Output 
Function 
 c Display a character. 
 s Display a sequence of characters until a terminating null \0 
 character is encountered. 
 37 
Data and Standard Output 
Function 
 Flags to supplement its output formatting capabilities, 
 placed immediately to the right of the percent sign 
 38 
Data and Standard Output 
Function 
 39 
Data and Standard Output 
Function 
 40 
41 
Data and Standard Output 
Function 
 42 
 Data and Standard Input 
 Function 
 Standard input function: scanf() 
  #include 
  Input the data from the standard input stream 
 A sequence of bytes flows from an input device: 
 keyboard, disk drive, network connection, and so on to 
 main memory. 
 Normally and automatically, the standard input stream 
 is connected to the keyboard. 
format-control-string describes the formats of the input. 
other-arguments are pointers to variables in which the input will be stored. 
 43 
 Data and Standard Input 
 Function 
The conversion specifiers used to input all types of data 
 44 
 Data and Standard Input 
 Function 
The conversion specifiers used to input all types of data 
 45 
 Data and Standard Input 
 Function 
The conversion specifiers used to input all types of data 
 Input data flow 
 from an input device 
 to main memory. 
 Input device = keyboard 
 Input 
 Input 
 Main memory ≈ variable ? 46 
 Data and Standard Input 
 Function 
 How to refer to the place in main memory 
 where the input data will be stored? 
  Memory is addressable contiguously. 
  Address is used! 
 Input a string: Input Input a character: A Input an integer: -123 
 Input device = keyboard Input device = keyboard Input device = keyboard 
 Input A -123 
 Input A -123 
 Main memory ≈ variable Main memory ≈ variable Main memory ≈ variable 
Varying size: user-predefined Fixed sizes: character = 1 byte, integer = 4 bytes, 47 
 Data and Standard Input 
 Function 
 Input a string: Input Input a character: A Input an integer: -123 
 Input device = keyboard Input device = keyboard Input device = keyboard 
 Input A -123 
 Input A -123 
 Main memory ≈ variable Main memory ≈ variable Main memory ≈ variable 
Varying size: user-predefined Fixed sizes: character = 1 byte, integer = 4 bytes,  
 char aString[5]; char aChar; int anInteger; 
 scanf(―%s‖, aString) scanf(―%c‖, &aChar) scanf(―%d‖, &anInteger) 
 printf(―%s‖, aString) printf(―%c‖, aChar) printf(―%d‖, anInteger) 
 In C, a string is defined as an array (sequence) of characters. The memory of this array 
 is referred by the address of the first character represented by the name of the array. 48 
Data and Standard Input 
Function 
 Put them altogether 
 49 
Data and Standard Input 
Function 
 Put them altogether 
 50 
Data and Standard Input 
Function 
 Input a date in the form of: dd/mm/yyyy 
 51 
Data and Standard Input 
Function 
 Input a date in the form of: dd Month yyyy 
 ??? 
 52 
Data Processing: Simple Example 
 Program for computing the distance between 
 the center and a given point in a 2D space 
  Input: x, y as a coordinate of a given point 
  Output: the distance along with the given point 
 on screen 
 y 
 (3, 2) 
 0 x 
 Distance (i.e. the length of 
 the blue line) = 3.605551 
 53 
Data Processing: Simple Example 
 Program for computing the distance between 
 the center and a given point in a 2D space 
  Input: x, y as a coordinate of a given point 
  Output: the distance along with the given point 
 on screen 
 54 
Data Processing: Simple Example 
 printf() stdio.h 
 Function calling: scanf() stdio.h 
 sqrt() math.h 
 system() stdlib.h 55 
 Summary 
 Start programming with the C language 
  The components of a standard C program 
  Input & Output vs. Read & Write vs. scanf & printf 
 Make your programs not only executable but 
 also readable 
  Coding styles 
 56 
Chapter 2: C Program Structure 
and its Components 
 57