Guide To UNIX Using Linux Third Edition

Presentation on theme: "Guide To UNIX Using Linux Third Edition"— Presentation transcript:

1 Guide To UNIX Using Linux Third Edition
Chapter 10: Developing UNIX/Linux Applications in C and C++ Guide To UNIX Using Linux Third Edition

2 Objectives Understand basic elements of C programming Debug C programs
Create, compile, and test C programs Use the make utility to revise and maintain source files Guide to UNIX Using Linux, Third Edition

3 Objectives (continued)
Identify differences between C and C++ programming Create a simple C++ program Create a C++ program that reads a text file Create a C++ program that demonstrates how C++ enhances C functions Guide to UNIX Using Linux, Third Edition

4 Introducing C Programming
C is the language in which UNIX was developed and refined C uses relatively short, isolated functions to break down large complex tasks into small and easily resolved subtasks C’s function-oriented design allows programmers to create their own functions to interact with the predefined system functions Guide to UNIX Using Linux, Third Edition

5 Creating a C Program A C program consists of separate bodies of code known as functions The functions call each other as needed and work to solve the problem for which the program was originally designed Guide to UNIX Using Linux, Third Edition

6 Creating a C Program (continued)
Guide to UNIX Using Linux, Third Edition

7 Creating a C Program (continued)
Guide to UNIX Using Linux, Third Edition

8 The C Library The core C language is very small
C library consists of functions for many common activities including: File, screen, and keyboard operations String operations Memory allocation and control Math operations Guide to UNIX Using Linux, Third Edition

9 Program Format A program includes 1 or more functions
Each program must have a main() function Format for main is: int main() { } Guide to UNIX Using Linux, Third Edition

10 Including Comments Comments begin with /* and end with */
Compiler ignores everything in the comment Comments can be anywhere in the file Guide to UNIX Using Linux, Third Edition

11 Using the Preprocessor #include Directive
Using the preprocessor #include directive allowed for the output shown here Guide to UNIX Using Linux, Third Edition

12 Specifying Data Types Guide to UNIX Using Linux, Third Edition

13 Specifying Data Types (continued)
Guide to UNIX Using Linux, Third Edition

14 Characters and Strings
Characters are represented internally in a single byte of computer memory Character constants must be enclosed in single quotes Strings are represented as arrays of characters String constants must be enclosed in double quotes Guide to UNIX Using Linux, Third Edition

15 Variables Variables must be declared before use
Declarations begin with a data type followed by one or more variable names The scope of a variable is the part of the program in which the variable is accessible Global variables can be accessed anywhere within a program Guide to UNIX Using Linux, Third Edition

16 Using Math Operators Guide to UNIX Using Linux, Third Edition

17 Generating Formatted Output with printf()
The output of a simple C program Guide to UNIX Using Linux, Third Edition

18 Generating Formatted Output with printf() (continued)
Guide to UNIX Using Linux, Third Edition

19 Using the C Compiler Command for C compiler in Linux is gcc
In some UNIX systems, it is cc Default executable file produced is a.out Specify another name using the –o option Information on options and use available at man gcc Guide to UNIX Using Linux, Third Edition

20 if Statements and C Loops
Use if statements to allow the program to make decisions depending on whether a condition is true or false Three looping mechanisms: for loop while loop do-while loop Guide to UNIX Using Linux, Third Edition

21 Using C Loops A C for loop generated the output in this program
Guide to UNIX Using Linux, Third Edition

22 Defining Functions When a function is defined, its name is declared and its statements are written The data type of the return value must be declared in the function definition Or “void” if no return value Function prototypes must be included in programs to tell the compiler about functions that will be defined later Guide to UNIX Using Linux, Third Edition

23 Using Function Arguments
A value passed to a function is an argument Arguments are stored in special automatic variables Can be referred to from anywhere in the function Guide to UNIX Using Linux, Third Edition

24 Using Function Return Values
Functions can return values Returned values can be used in assignment statements such as y=triple(x) Must declare the type of the return value in the function definition Guide to UNIX Using Linux, Third Edition

25 Working with Files in C Files are continuous streams of data
Typically stored on disk File pointers point to predefined structures that contain information about the file Before using a file, it must be opened The library function for this is fopen When done with a file, it must be closed The library function for this is fclose Guide to UNIX Using Linux, Third Edition

26 Working with Files in C (continued)
File I/O uses various library functions fgetc performs character input fputc performs character output During an input operation, it is essential to test for the end of a file feof tests for the end-of-file marker Guide to UNIX Using Linux, Third Edition

27 Using the make Utility to Maintain Program Source Files
Some programs have many files of source code Once compiled, the separate object files are linked into executable code As program is updated, only need to recompile files that have changed Guide to UNIX Using Linux, Third Edition

28 Using the make Utility to Maintain Program Source Files (continued)
make utility helps tracks what needs to be recompiled by using the time stamp field for each source file A control file, called the makefile, lists the source files and their relationship to each other Guide to UNIX Using Linux, Third Edition

29 Using the make Utility to Maintain Program Source Files (continued)
The make utility follows a set of rules General rule definition includes A target file One or more dependencies An action that creates the target Guide to UNIX Using Linux, Third Edition

30 Debugging Your Program
The compiler identifies some types of errors in a program Common errors include: incorrect syntax, missing semicolons, case-sensitive errors Steps to correct syntax errors: Write down the error Edit the source file Save and recompile the file Guide to UNIX Using Linux, Third Edition

31 Creating a C Program to Accept Input
Use the scanf function to accept input from the keyboard scanf uses a control string with format specified in a manner similar to printf scanf can accept multiple inputs, but remember that this can lead to difficult and cumbersome code Guide to UNIX Using Linux, Third Edition

32 Creating a C Program to Accept Input (continued)
Guide to UNIX Using Linux, Third Edition

33 Creating a C Program to Accept Input (continued)
Guide to UNIX Using Linux, Third Edition

34 Creating a C Program to Accept Input (continued)
An example of using C to accept keyboard input Guide to UNIX Using Linux, Third Edition

35 Introducing C++ Programming
C++ adds object-oriented capabilities to C C and C++ are similar in many ways C++ uses functions, as does C, but includes the use of functions as methods for objects Guide to UNIX Using Linux, Third Edition

36 Introducing C++ Programming (continued)
The major differences between C and C++ C follows procedural principles, whereas C++ follows object-oriented principles C++ introduces “objects” A collection of data and a set of operations called methods to manipulate the data Guide to UNIX Using Linux, Third Edition

37 Creating a Simple C++ Program
Using C++ instead of C to create a program Guide to UNIX Using Linux, Third Edition

38 How C++ Enhances C Functions
Function overloading allows C++ to use the same function name for different types of arguments Guide to UNIX Using Linux, Third Edition

39 Chapter Summary C programs often consist of separate files called program modules that are compiled separately into object code and linked together to make up the program The core C language is small, relying on libraries for extended functionality UNIX was developed and refined in C Guide to UNIX Using Linux, Third Edition

40 Chapter Summary (continued)
A compiler translates source code into object code A linker links all object code files plus library functions into an executable file The make utility maintains source files Only changed files need to be recompiled Guide to UNIX Using Linux, Third Edition

41 Chapter Summary (continued)
C is procedural and C++ is object-oriented Function overloading: C++ offers a way to define a function to handle multiple sets of arguments Guide to UNIX Using Linux, Third Edition