Difference between while loop and do loop?

Answer 1

The difference between "do while" and "do until" is that a "do while" loops while the test case is true, whereas "do until" loops UNTIL the test case is true (which is equivalent to looping while the test case is false).

The difference between a "do ...while" loop and a "while {} " loop is that the while loop tests its condition before execution of the contents of the loop begins; the "do" loop tests its condition after it's been executed at least once. As noted above, if the test condition is false as the while loop is entered the block of code is never executed. Since the condition is tested at the bottom of a do loop, its block of code is always executed at least once.

To further clear your concept on this, understand the syntax and description of the two loop types:

while
The while loop is used to execute a block of code as long as some condition is true. If the condition is false from the start the block of code is not executed at al. The while loop tests the condition before it's executed so sometimes the loop may never be executed if initially the condition is not met. Its syntax is as follows.

while (tested condition is satisfied)
{
block of code
}

In all constructs, curly braces should only be used if the construct is to execute more than one line of code. The above program executes only one line of code so it not really necessary (same rules apply to if...else constructs) but you can use it to make the program seem more understandable or readable.

Here is a simple example of the use of the while loop. This program counts from 1 to 100.

#include

int main(void)
{

int count = 1;

while (count <= 100)
{
printf("%d\n",count);
count += 1; // Notice this statement
}

return 0;

}

Note that no semi-colons ( ; ) are to be used after the while (condition) statement. These loops are very useful because the condition is tested before execution begins. However i never seem to like these loops as they are not as clear to read as the do ...while loops. The while loop is the favorite amongst most programmers but as for me, i definitely prefer the do ...while loop.

do ....while
The do loop also executes a block of code as long as a condition is satisfied.

Again, The difference between a "do ...while" loop and a "while {} " loop is that the while loop tests its condition before execution of the contents of the loop begins; the "do" loop tests its condition after it's been executed at least once. As noted above, if the test condition is false as the while loop is entered the block of code is never executed. Since the condition is tested at the bottom of a do loop, its block of code is always executed at least once.

Some people don't like these loops because it is always executed at least once. When i ask them "so what?", they normally reply that the loop executes even if the data is incorrect. Basically because the loop is always executed, it will execute no matter what value or type of data is supposed to be required. The "do ....while" loops syntax is as follows

do
{
block of code
} while (condition is satisfied);

Note that a semi-colon ( ; ) must be used at the end of the do ...while loop. This semi-colon is needed because it instructs whether the while (condition) statement is the beginning of a while loop or the end of a do ...while loop. Here is an example of the use of a do loop.

include

int main(void)
{

int value, r_digit; printf("Enter a number to be reversed.\n");
scanf("%d", &value); do
{
r_digit = value % 10;
printf("%d", r_digit);
value = value / 10;
} while (value != 0); printf("\n"); return 0;

}

Answer 2

While LoopDo...While LoopEntry-Controlled LoopExit-Controlled LoopLoop Condition has to be initially

TRUE for body to be executedLoop body will be executed at-least onceInitialization, Condition, Update

Statements are to be written SeparatelyInitialization, Condition, Update

Statements are to be written SeperatelySyntax :

while(condition){

statement...

statement...

}Syntax :

do{

statement...

statement...

} while(condition);

Answer 3

A do loop will always execute at least once because the condition check is at the end of the do loop. The loop continues until the condition is false.

do

{

....

....

}

while(a==1);

A while loops checks the condition first and will not execute if the condition is false.

while (a==1)

{

....

....

}

Answer 4

well, the two can be converted into each other:

in: do stmt while (exp);

out: stmt; while (exp) stmt

or: first= 1; while (first exp) { first= 0; stmt }

in: while (exp) stmt

out: if (exp) do stmt while (exp);

Answer 5

while() {} the body of this loop will be executed if only expression in brackets are not zero (false). Expression is checked before executing body of loop.

while do {} while() it is very similar to while() loop described above, but the difference is that at least once the body will be executed and after execution expression in brackets is checked.

Examples

while (num < 10) {

printf("%d\n", ++num);

}

int num = 0;

do {

printf("%d\n", ++num);

} while (num < 10);

Both examples produces numbers from 1 to 10.

Answer 6

difference between c an cpp

** Assuming you mean what's the difference between the two... The while loop will only execute if the condition evaluates as true. The do-while will execute at least once, regardless.

EXAMPLE:

while(DAD_IS_HAPPY) { Give me money }

...in this example, as long as Dad is happy, he'll give me money. If he's not happy, I won't get any money.

do { Give me money

}while(DAD_IS_HAPPY)

in this case, I will get money first, then it checks to see if dad is happy. If he is happy, I'll keep getting money. If he's not happy, I'll still get money that very first time :)

Answer 7

There is nothing like do loop.its while loop.
in case of while loop as the condition is given at first,the condition is checked first n then if true the body is executed.But in case of do-while loop.first time the condition is escaped as it is given after the body of the loop.n then same as while loop.

Answer 8

The while loop evaluates the loop expression first. If it is true, the loop body executes, and then the loop iterates with the loop expression. If the expression is initially false, the loop body will never execute.

The do while loop evaluates the loop body first, then it evaluates the loop expression. If it is true, the loop iterates with the loop body. The loop body will execute at least one time, no matter what the outcome of the loop expression.

Answer 9

for a do while loop the statements are executed at least one since the statements are executed before they are executed,but for a do loop the statements are first evaluated then executed there they may not necessarily executed

Answer 10

The while loop tests the condition at the top, while the do while loop tests the condition at the bottom. If the condition is initially false, the while loop will never execute, while the do while loop will execute once.