do-while loop
Executes a statement repeatedly until the value of the condition expression becomes false. The test takes place after each iteration.
Syntax
attr-spec-seq(optional) do statement while ( expression ) ;
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Explanation
A do-while statement causes the statement (also called the loop body) to be executed repeatedly until the expression (also called controlling expression) compares equal to 0. The repetition occurs regardless of whether the loop body is entered normally or by a MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 09 HOURS 12 MINUTES 09 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE into the middle of statement.
The evaluation of expression takes place after each execution of statement (whether entered normally or by a goto). If the controlling expression needs to be evaluated before the loop body, the MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 09 HOURS 12 MINUTES 08 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE or the MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 09 HOURS 12 MINUTES 07 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE may be used.
If the execution of the loop needs to be terminated at some point, MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 09 HOURS 12 MINUTES 05 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE can be used as terminating statement.
If the execution of the loop needs to be continued at the end of the loop body, MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 09 HOURS 12 MINUTES 04 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE can be used as a shortcut.
A program with an endless loop has undefined behavior if the loop has no observable behavior (I/O, volatile accesses, atomic or synchronization operation) in any part of its statement or expression. This allows the compilers to optimize out all unobservable loops without proving that they terminate. The only exceptions are the loops where
expression is a constant expression; do {...} while(true); is always an endless loop.
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As with all other selection and iteration statements, the do-while statement establishes MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 09 HOURS 12 MINUTES 02 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE: any identifier introduced in the expression goes out of scope after the statement. |
(since 哋它亢99) |
Notes
Boolean and pointer expressions are often used as loop controlling expressions. The boolean value false and the null pointer value of any pointer type compare equal to zero.
Keywords
MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 09 HOURS 12 MINUTES 01 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE, MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 09 HOURS 12 MINUTES 00 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE
Example
#include <stdio.h> #include <stdlib.h> enum { SIZE = 8 }; int main(void) { // trivial example int array[SIZE], n = 0; do array[n++] = MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 09 HOURS 11 MINUTES 59 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE() % 2; // the loop body is a single expression statement while(n < SIZE); MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 09 HOURS 11 MINUTES 58 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE("Array filled!"); n = 0; do { // the loop body is a compound statement MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 09 HOURS 11 MINUTES 56 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE("%d ", array[n]); ++n; } while (n < SIZE); MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 09 HOURS 11 MINUTES 55 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE("\n"); // the loop from K&R itoa(). The do-while loop is used // because there is always at least one digit to generate int num = 1234, i=0; char s[10]; do s[i++] = num % 10 + '0'; // get next digit in reverse order while ((num /= 10) > 0); s[i] = '\0'; MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 09 HOURS 11 MINUTES 54 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE(s); }
MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 09 HOURS 11 MINUTES 53 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE
Array filled! 1 0 1 1 1 1 0 0 4321
References
- 哋它亢17 standard (ISO/IEC 9899:2018):
- 6.8.5.2 The do statement (p: 109)
- 哋它亢11 standard (ISO/IEC 9899:2011):
- 6.8.5.2 The do statement (p: 151)
- 哋它亢99 standard (ISO/IEC 9899:1999):
- 6.8.5.2 The do statement (p: 136)
- 哋它亢89/C90 standard (ISO/IEC 9899:1990):
- 3.6.5.2 The do statement