Break in C

7 Key excerpts on "Break in C"

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  eBook - ePub

  Learn C Programming from Scratch

  A step-by-step methodology with problem solving approach (English Edition)

  • Mohammad Saleem Mir(Author)
  • 2024(Publication Date)
  • BPB Publications

    (Publisher)

  goto are C’s three primary loop control statements.

  Break

  The break statement is used to control the flow of control structures like loops, conditional statements, and branching statements. When the break statement is encountered, the program instantly halts the control structure’s execution, in which the break has been used, and execution moves on to the code that follows the control structure. break statement is generally used to terminate loops or switch statements.

  • Break example 1:
    #in clude <stdio.h>
    int main () { int i; for (i=1; i<=10; i++) { if (i == 2) { break; } printf("%d\t", i); } printf("\nbye"); return (0); } Output: 1 Bye

  In this program, as soon as condition if(i==2) evaluates to true, control will come out of the for loop and the printf() instruction will get executed, before ending execution of the main() function.

  • Break example 2: #include <stdio.h> int main () { int n1, n2; do { printf("Input 2 numbers\n"); scanf ("%d%d", &n1,&n2); if (n2 == 0) { printf("Cannot Divide by Zero\n"); break; } printf("Quotient = %d\n", n1/ n2); printf("Press y to continue\n"); } while (getche()=='y'); return (0); }

  In this program, if user inputs 0 as the second number, the corresponding if statement evaluates to true, break will force control to come out of the do-while loop.

  Continue

  The continue statement is used to go to the next iteration of a loop without running the remaining code in the current iteration. The control variable for the loop is updated and the loop condition is re-evaluated when the continue

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  You Can Program in C++

  A Programmer's Introduction

  • Francis Glassborow(Author)
  • 2006(Publication Date)
  • Wiley

    (Publisher)

  Most C idioms will work in C++, but every one of them needs to be re-examined in the context of C++, because not all of them are the preferred option in C++. break , continue , and goto There are several ways of varying from the normal flow of code in a construct. I am leaving the details of return until Chapter 5, when I deal with functions. You will also have noted that throwing an exception exits from the normal flow. I am also leaving details of that for a later chapter. I have already made extensive use of break without going into much detail as to what it does. break causes an immediate exit from any of the above loop constructs ( for , while , and do-while ) as well as forcing an exit from a switch statement (and an if statement, but you should generally avoid its use there). The statement immediately after the construct in question will be the next one executed after a break statement. It is good practice to avoid using break for exiting loops, though we have seen one of the exceptions to this in its use for exiting an otherwise infinite loop. It is often possible to change the source code so that break is unnecessary. The resulting code is often simpler even if it was not so obvious in the first place. If you find yourself writing more complicated code in order to avoid an early exit from a loop, you are probably heading in the wrong direction. Often programmers are still using a mental model that involves early exit while trying to abide by a coding guideline that prohibits the use of break . Try to design your code so that an early exit from a loop is unnecessary. Then you will reduce your use of break for all the right reasons, and your code will likely become simpler and more elegant. Sometimes we find that we need to abandon the current pass of a loop and go immediately to the next one. C++ provides a special mechanism for that: the keyword continue .

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  Computer Programming with C++

  • Kunal Pimparkhede(Author)
  • 2017(Publication Date)
  • Cambridge University Press

    (Publisher)

  Hence break statement, in C/ C++ can be used to break the switch block or it can be used to break the loop . However, continue statement is designed to operate only with loops and it will make no sense to use it with any of the decision making control structures like switch block for example. Will the break statement terminate if it is written within the switch block which is inside the loop? ? If the switch block is present inside the loop and if the break statement is written within the switch block, it will only exit the switch block and not the loop. For example, consider pseudo code below: while(Looping condition ) { switch(expression) { case Value 1: operation 1; break; case Value 2:operation 2; break; …… .. default: default operation; } } If you intend to terminate the loop, in this case, you must write the break statement outside the switch block. Similarly, if there is a nesting of loops in your program, the break statement will only terminate the inner most loop in which it is written. Do not expect the break statement to terminate all the loops together. As shown below, there are three while loops one inside another and the break statement is written in the innermost loop. In this case, the break statement will only terminate the inner most loop and the execution of outer loops will continue as usual while(Looping condition 1) { while(condition 2) { while(condition 3) { ........ ........ break; ........ ........ } } }  5.5.1 To check if the number is prime or not: An example Let us write a program to take a number as input from the user and to check if the number is prime of not. Iterative Control Statements: Loops ✦ 189 We know that any number x is a prime number if it is divisible by exactly two numbers 1 and x itself. Hence, for a given number x we will generate all the numbers from 2 to x-1 in our code, and we can easily conclude that x is prime if it is divisible by no number between 2 and x-1 .

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  Programming Microcontrollers in C

  • Ted VanSickle(Author)
  • 2001(Publication Date)
  • Newnes

    (Publisher)

  Break can be used to exit for , while , do -while , and switch statements. An example of the use of the break statement is shown in the next section. The continue statement causes the next iteration of a for , w h ile, or a do while loop to be started. In the case of the for statement, the last argument is executed, and control is passed to the beginning of the for loop. For both the while and the do -while , the argument of the while statement is tested immediately, and the program proceeds according to the result of the test. The break statement is seen frequently, and the continue statement is rarely used. Another statement that is even more rarely used is the goto . In C, the programmer can create a label at any location by typing the label name followed by a colon. If it is neces-sary, the goto < label > can be used to transfer control of the program from one location to another. In general, C provides enough structured language forms that the use of the goto < label > se-quence will rarely be needed. One place where the goto can be used effectively is when the program is nested deeply and an error is detected. In such a case, the goto statement is an effective means of unwinding the program from a deep loop to an outer loop to process the error. In general, you should avoid goto statements whenever possible. That said, there is an excellent alternative to a goto . The reach of a goto is limited to the function in which it is defined. In fact, the reach should probably be confined to the block in which it is de-fined. Since new variables can be defined at the beginning of any block, undefined behavior can be introduced when a goto branches into a block where new variables have been defined. Also, you can introduce undefined behavior when you branch out of a block where 49 variables have been defined. In both cases, the branch is around op-erations of defining or deleting local variables. The alternative is to make use of the setjmp() and longjmp() functions.

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  eBook - PDF

  C++ Programming

  From Problem Analysis to Program Design

  • D. Malik(Author)
  • 2017(Publication Date)
  • Cengage Learning EMEA

    (Publisher)

  (After executing the break statement in a loop, the remaining statements in the loop are discarded.) Copyright 2016 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Nested Control Structures | 315 5 The break statement is an effective way to avoid extra variables to control a loop and produce an elegant code. However, break statements must be used very sparingly within a loop. An excessive use of these statements in a loop will produce spaghetti-code (loops with many exit conditions) that can be very hard to understand and manage. You should be extra careful in using break statements and ensure that the use of the break statements makes the code more readable and not less readable. If you’re not sure, don’t use break statements. The continue statement is used in while, for, and do. . .while structures. When the continue statement is executed in a loop, it skips the remaining statements in the loop and proceeds with the next iteration of the loop. In a while and do. . .while struc- ture, the expression (that is, the loop-continue test) is evaluated immediately after the continue statement. In a for structure, the update statement is executed after the continue statement, and then the loop condition (that is, the loop-continue test) executes. If the previous program segment encounters a negative number, the while loop ter- minates.

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  Basic Data Structures and Program Statements

  • Xingni Zhou, Qiguang Miao, Lei Feng(Authors)
  • 2020(Publication Date)
  • De Gruyter

    (Publisher)

  224 5 Program statements loop. In other words, the remaining statements in the current iteration are skipped and the next iteration is started. 5.9.2 Jumping out of loops with break statement To address requirements in practice, C provides the break statement for terminating loops in advance as shown in Figure 5.85. In fact, we have seen its usage when in-troducing the syntax of switch statement. Example 5.22 Analysis of the variant of “ things whose number is unknown ” problem What is the maximum number within 2000 that has remainder 2 when divided by 3, has remain-der 3 when divided by 5, and has remainder 2 when divided by 7? Write two programs using while and for, respectively. [Analysis] 1. Algorithm design This is a process of repeatedly testing whether an integer satisfies the given condition: we start from x = 2000, test whether x satisfies the condition and decrease its value repeatedly. Once we have found the solution, we jump out of the loop. As we do not know what range the solution lies in, we cannot determine the execution condition. Figure 5.86 shows the key elements of the loop and pseudo code. Increment T Statement set 1 break Statement set 2 Condition End of loop F break can be used in switch statements as well Execution condition Initial value Figure 5.85: Break statement in loop structure. 5.9 Interruption of loops 225 Top-level pseudo code Refinement x starts from 2000 x= 2000 while () while () decrease x by 1 if x doesn’t satisfy given conditions. Repeat until finding an x that satisfies the conditions if x%3==2 and x%5==3 an x%7==5 break x-- ; Output x Output x Initial condition x=2000 Execution condition Unknown Increment x-- Figure 5.86: Algorithm description of things whose number is unknown problem. Note that the loop increment in this example is decreasing. Increment here means the change of the loop control variable, which can be increasing or decreasing, regular or irregular.

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  eBook - ePub

  Scientific Programming: C-language, Algorithms And Models In Science

  C-Language, Algorithms and Models in Science

  • Luciano Maria Barone, Enzo Marinari, Giovanni Organtini, Federico Ricci Tersenghi(Authors)
  • 2013(Publication Date)
  • WSPC

    (Publisher)

  In this example, the initial value of option is completely irrelevant. In-deed, once the program has reached line 7, it executes the lines between curly brackets anyway, thus acquiring the value of option from the keyboard. The condition on line 11 is true on the whole if and only if option assumes a value different from the expected ones. In this case, a message inviting the user to repeat the input is printed on the screen. The same condition is included in the do-while construct, and if the user made a mistake, the lines between curly brackets are executed again. This continues until the user correctly selects either 1 or 2. In cases like these, the break statement may be included to make the code more compact and clear (Listing 4.5).

  Listing 4.5 Use of break.

  As soon as the condition on line 5 occurs (i.e., when the user selects a correct option) the cycle is interrupted at the break statement. The latter generates a jump to the statement following the while, which therefore no longer needs to contain a condition depending on what takes place inside the cycle. As mentioned before, some consider the use of the break statement unfortunate and it can actually easily be replaced by an alternative and, to some degree, more elegant technique as the one of Listing 4.6.

  Listing 4.6 Alternative to the break statement.

  C does not provide a type representing only logical values. Therefore, they are represented by character variables as these occupy the least memory space (8 bit). By defining the variable incorrectlnput which is set to true until the user does not insert a valid character, we can write the cycle as in the Listing 4.6.

  C provides yet another statement to perform an iterative cycle, namely the for statement. The syntax of this statement is as follows: or, adopting a more readable style: This construct is fully equivalent to the following:

  Indeed, first the value of expression_1 is evaluated. Next, if the logical value of expression_2 is true, the statement is executed (remember the final semicolon), before expressions is evaluated. Of course, evaluating the expressions might require the execution of some statements.

  Though all iteration structures are interchangeable, the for construct is preferred in cycles controlled by the value of a variable representing an index or counter. In these cases the number of times the statements should be repeated is known beforehand.

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