Search results
Results From The WOW.Com Content Network
Do while loops check the condition after the block of code is executed. This control structure can be known as a post-test loop. This means the do-while loop is an exit-condition loop. However a while loop will test the condition before the code within the block is executed.
In the C programming language, Duff's device is a way of manually implementing loop unrolling by interleaving two syntactic constructs of C: the do-while loop and a switch statement. Its discovery is credited to Tom Duff in November 1983, when Duff was working for Lucasfilm and used it to speed up a real-time animation program.
If xxx1 is omitted, we get a loop with the test at the top (a traditional while loop). If xxx2 is omitted, we get a loop with the test at the bottom, equivalent to a do while loop in many languages. If while is omitted, we get an infinite loop. The construction here can be thought of as a do loop with the while check in the middle. Hence this ...
Because the while loop checks the condition/expression before the block is executed, the control structure is often also known as a pre-test loop. Compare this with the do while loop , which tests the condition/expression after the loop has executed.
while The while keyword is used to create a while loop, which tests a boolean expression and executes the block of statements associated with the loop if the expression evaluates to true; this continues until the expression evaluates to false. This keyword can also be used to create a do-while loop; see do. [11] [12]
Despite the seemingly greater complexity of the second example, it may actually run faster on modern CPUs because they use an instruction pipeline. By nature, any jump in the code causes a pipeline stall, which is a detriment to performance. Additionally, loop inversion allows safe loop-invariant code motion.
Get AOL Mail for FREE! Manage your email like never before with travel, photo & document views. Personalize your inbox with themes & tabs. You've Got Mail!
Loop-invariant code consists of statements or expressions that can be moved outside a loop body without affecting the program semantics. Such transformations, called loop-invariant code motion, are performed by some compilers to optimize programs. A loop-invariant code example (in the C programming language) is