Chapter - Advanced C Topics, PPT, PF, Semester, Engineering - Computer Science Engineering (CSE) PDF Download

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Introduction

The slides cover the following topics:

14.1  Introduction 

14.2  Redirecting Input/Output on UNIX and DOS Systems

14.3  Variable-Length Argument Lists 

14.4  Using Command-Line Arguments 

14.5  Notes on Compiling Multiple-Source-File Programs

14.6  Program Termination with exit and atexit 

14.7  The volatile Type Qualifier 

14.8  Suffixes for Integer and Floating-Point Constants 

14.9  More on Files 

14.10  Signal Handling 

14.11  Dynamic Memory Allocation with calloc and   realloc

14.12  The Unconditional Branch: goto 

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14.1   Introduction

•Standard I/O - keyboard and screen

–Redirect input and output

 

•Redirect symbol(<)

–Operating system feature, not a C feature

–UNIX and DOS

–$ or % represents command line

–Example:

$ myProgram < input

–Rather than inputting values by hand, read them from a file

 

•Pipe command(|)

–Output of one program becomes input of another

$ firstProgram | secondProgram

–Output of firstProgram goes to secondProgram

 

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 14.2   Redirecting Input/Output on UNIX and DOS Systems 

 

•Redirect output (>)

–Determines where output of a program goes

–Example:

$ myProgram > myFile

•Output goes into myFile (erases previous contents)

 

•Append output (>>)

–Add output to end of file (preserve previous contents)

–Example:

$ myOtherProgram >> myFile

 

•Output is added onto the end of myFile

 

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14.3   Variable-Length Argument Lists

 

 

•Functions with unspecified number of arguments

–Load <stdarg.h>

–Use ellipsis(...) at end of parameter list

–Need at least one defined parameter

–Example:

double myfunction ( int i, ... );

–The ellipsis is only used in the prototype of a function with a variable length argument list

–printf is an example of a function that can take multiple arguments

–The prototype of printf is defined as

int printf( const char* format, ... );

 

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14.3  Variable-Length Argument Lists

 

 

•Macros and definitions of the variable arguments header (stdarg.h)

–va_list

 

•Type specifier, required (va_list arguments;)

–va_start( arguments, other variables )

 

•Intializes parameters, required before use

–va_arg( arguments, type )

 

•Returns a parameter each time va_arg is called 

 

•Automatically points to next parameter

–va_end( arguments )

 

•Helps function have a normal return

 

 

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14.4   Using Command-Line Arguments

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14.5   Notes on Compiling Multiple-Source-File Programs

• extern int myGlobal;

•Keyword static

 

 •Specifies that variables can only be used in the file in which they are defined

 

•Programs with multiple source files

 

 •Tedious to compile everything if small changes have been made to only one file

 

 •Can recompile only the changed files

 

•Procedure varies on system

 •UNIX: make utility

 

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14.6   Program Termination with exit and atexit

 

•Function exit

•Forces a program to terminate

•Parameters – symbolic constants EXIT_SUCCESS or EXIT_FAILURE

•Returns an implementation-defined value

•Example:

exit( EXIT_SUCCESS );

•Function atexit

atexit( functionToRun );

•Registers functionToRun to execute upon successful program termination

•atexit itself does not terminate the program

•Register up to 32 functions (multiple atexit() statements)

•Functions called in reverse register order

•Called function cannot take arguments or return values

 

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