### 25.3.5 While loop

The while-loop is used to repeat a code block as long as a given condition holds. To use it, enter while, the condition in parentheses, and then a code block.

while (boolean) block

#### Example

Add the terms of the harmonic series 1+1/2+1/3+1/4+⋯ until a term is less than 0.05.

You can initialize the sum S to 0 and let j be the first term 1. Input:

S:=0; j:=1

Then use a while loop.

while (1/j>=0.05) { S:=S+1/j; j:=j+1; }

or:

tantque (1/j>=0.05) faire S:=S+1/j; j:=j+1; ftantque

then:

S

55835135
15519504

Note that a while loop can also be written as a for loop. For example, as long as S is set to 0 and j is set to 1, the above loop can be written as

for (;1/j>=0.05;) { S:=S+1/j; j:=j+1; }

or, with only S set to 0,

for (j:=1; 1/j>=0.05; j++) { S:=S+1/j; }

which, of course, yields the same result.