Page 22 - Programming Microcontrollers in C

Some Simple Programs 7

executed. The argument should be read “i is less than 11.” The ini­
tially assigned value for i was 1, so the argument is TRUE. The
compound statement

{
printf(“\t%d\t%d\t%d\n”, i, i*i,i*i*i);
i=i+1;
}

will start execution with the value of i being equal to 1. Once this
statement is evaluated, control is passed back to the while and its
argument is evaluated. If the argument is TRUE, the statement fol­
lowing will be evaluated again. This sequence will repeat until the
argument evaluates as FALSE.
In this expression, the string argument of the printf function
contains three %d commands. Each %d command causes the corre­
sponding argument following the string to be printed to the screen.
There are tab characters, \t, to separate the various printed values
on the screen. The first %d will cause the value of i to be printed
2
on the screen. The second %d will cause the value i*i, or i , to
be printed to the screen. The third %d will print the value of i*i*i,
3
or i to be printed. When C executes the function call, the values
of the arguments are calculated prior to the call, so arguments like
i*i are evaluated by the calling program and passed by value to
the function.
The statement
i=i+1;

is an example of the use of both precedence and association—the
direction in which expressions are evaluated—in C. The equal sign
here is an operator just like the + symbol. The + operator is evaluated
from left to right, and the = operator is evaluated from right to left.
Also, the + operator has higher precedence than the = operator. There­
fore, the above statement will add one to the value stored in i and
then assign this new value to the variable i. This expression simply
increments the variable i.
The above statement is the terminating statement of the com­
pound statement following the while. Since i had an initial value
of 1, control will be returned to the while with a value of 2 for i. 2,