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What Is a Pointer?
A pointer is a variable whose value is used to point to another variable.
From this definition, you know two things: first, that a pointer is a variable, so you can assign different values to a pointer variable, and second, that the value contained by a pointer must be an address that indicates the location of another variable in the memory. That’s why a pointer is also called an address variable.
Address (Left Value) Versus Content (Right Value)
To help solidify your understanding of this hour’s lesson, you are encouraged to answer the quiz questions and finish the exercises provided in the Workshop before you move to the next lesson. The answers and hints to the questions and exercises are given in Appendix E, “Answers to Quiz Questions and Exercises.”
Quiz
Given x = 0, will the arithmetic operations inside the following if statement be performed?
if (x != 0)
y = 123 / x + 456;
Question and Answer
Q How many expressions are there in the if statement?
A The if statement takes only one expression to hold the conditional criteria. When the expression is true (that is, the conditions are met), the statements controlled by the if statement are executed. Otherwise, the next statement following the if statement block is executed.
Q Why is the if-else statement an expansion of the if statement?
The goto Statement
I feel that this book would not be not complete without mentioning the goto statement, although I do not recommend that you use the goto statement unless it’s absolutely necessary. The main reason that the goto statement is discouraged is because its usage may make the C program unreliable and hard to debug.
The following is the general form of the goto statement:
labelname:
statement1;
statement2;
.
.
.
goto labelname;
The continue Statement
Instead of breaking a loop, there are times when you want to stay in a loop but skip over some statements within the loop. To do this, you can use the continue statement provided by C. The continue statement causes execution to jump to the top of the loop immediately.
You should be aware that using the continue statement, as well as the break statement, may make your program hard to debug.
For example, Listing 10.7 demonstrates how to use the continue statement in a loop doing sums.
The break Statement
You can add a break statement at the end of the statement list following every case label, if you want to exit the switch construct after the statements within a selected case are executed.
The program in Listing 10.5 does a similar job as the one in Listing 10.4, but this time, the break statement is used.
TYPE
Listing 10.5. Adding the break statement.
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