Programming and Graphics

3.3 Control structures 57

For example, consider the block of commands:

goto mark;

a=5;

mark:

The statementa=5will be skipped.

Fortran 77users are fondly familiar with theGo tostatement.Mat-

labusers are unfairly deprived of this statement.

Some programmers consider thegotostatement an anathema and a recipe

for “spaghetti code.” In the opinion of this author, this is only an exag-

geration.

• while loop:

We use thewhileloop to execute a block of commands only when a

distinguishing condition is true.

For example, the followingwhileloop prints the integers: 1, 2, ..., 9,

10:

int i=0;

while(i<10)

{

i=i+1;

cout<<i<<"";

}

Note that the veracity of the distinguishing conditioni<10is checked

beforeexecuting the loop enclosed by the curly brackets.

The compiler interprets the expressioni<10as a Boolean variable that is

true, and thus equal to 1, or false, and thus equal to 0. Accordingly, the

loop

int i=1;

while(i)

{

i=i-1;

}

will be executed only once.