how create barcode in excel 2010 Page 82 in Software

Creation Quick Response Code in Software Page 82

The initialization section has been left blank, and x is initialized before the loop is entered The Infinite Loop Although you can use any loop statement to create an infinite loop, for is traditionally used for this purpose Since none of the three expressions that form the for loop are required, you can make an endless loop by leaving the conditional expression empty, as here:

for( ; ; ) printf("This loop will run forever\n");

When the conditional expression is absent, it is assumed to be true You may have an initialization and increment expression, but C programmers more commonly use the for(;;) construct to signify an infinite loop Actually, the for(;;) construct does not guarantee an infinite loop because a break statement, encountered anywhere inside the body of a loop, causes immediate termination (break is discussed in detail later in this chapter) Program control then resumes at the code following the loop, as shown here:

ch = '\0'; for( ; ; ) { ch = getchar(); /* get a character */ if(ch == 'A') break; /* exit the loop */ } printf("you typed an A");

This loop will run until the user types an A at the keyboard for Loops with No Bodies A statement may be empty This means that the body of the for loop (or any other loop) may also be empty You can use this fact to simplify the coding of certain algorithms and to create time delay loops Removing spaces from an input stream is a common programming task For example, a database program may allow a query such as ''show all balances less than 400" The database needs to have each word fed to it separately, without leading spaces That is, the database input processor recognizes "show" but not "show" The following loop shows one way to accomplish this It advances past leading spaces in the string pointed to by str

Page 83 for( ; *str == ' '; str++) ;

As you can see, this loop has no body and no need for one either Time delay loops are sometimes useful The following code shows how to create one by using for:

for(t=0; t < SOME_VALUE; t++) ;

The only purpose of this loop is to eat up time Be aware, however, that some compilers will optimize such a time delay loop out of existence, since (as far as the compiler is concerned) it has no effect! So, you might not always get the time delay you expect Declaring Variables within a for Loop In C99 and C++, but not C89, it is possible to declare a variable within the initialization portion of a for loop A variable so declared has its scope limited to the block of code controlled by that statement That is, a variable declared within a for loop will be local to that loop Here is an example that declares a variable within the initialization portion of a for loop:

/* Here, i is local to for loop; j is known outside loop *** This example is invalid for C89 *** */ int j; for(int i = 0; i<10; i++) j = i * i; /* i = 10; *** Error ***-- i not known here! */

Here, i is declared within the initialization portion of the for and is used to control the loop Outside the loop, i is unknown Since a loop control variable is often needed only by that loop, the declaration of a variable in the initialization portion of the for is becoming common practice Remember, however, that this is not supported by C89 The while Loop The second loop available in C is the while loop Its general form is while(condition) statement;