All programs have bugs. The bigger the program, the more bugs, and many of those bugs actually "get out the door" and into final...
All programs have bugs. The bigger the program, the more bugs, and many of those bugs actually "get out the door" and into final, released software. That this is true does not make it okay, and making robust, bug-free programs is the number-one priority of anyone serious about programming.
The single biggest problem in the software industry is buggy, unstable code. The biggest expense in many major programming efforts is testing and fixing. The person who solves the problem of producing good, solid, bulletproof programs at low cost and on time will revolutionize the software industry.
There are a number of discrete kinds of bugs that can trouble a program. The first is poor logic: The program does just what you asked, but you haven't thought through the algorithms properly. The second is syntactic: You used the wrong idiom, function, or structure. These two are the most common, and they are the ones most programmers are on the lookout for.
Research and real-world experience have shown beyond a doubt that the later in the development process you find a problem, the more it costs to fix it. The least expensive problems or bugs to fix are the ones you manage to avoid creating. The next cheapest are those the compiler spots. The C++ standards force compilers to put a lot of energy into making more and more bugs show up at compile time.
Bugs that get compiled in but are caught at the first test--those that crash every time--are less expensive to find and fix than those that are flaky and only crash once in a while.
A bigger problem than logic or syntactic bugs is unnecessary fragility: Your program works just fine if the user enters a number when you ask for one, but it crashes if the user enters letters. Other programs crash if they run out of memory, or if the floppy disk is left out of the drive, or if the modem drops the line.
To combat this kind of fragility, programmers strive to make their programs bulletproof. A bulletproof program is one that can handle anything that comes up at runtime, from bizarre user input to running out of memory.
It is important to distinguish between bugs, which arise because the programmer made a mistake in syntax; logic errors, which arise because the programmer misunderstood the problem or how to solve it; and exceptions, which arise because of unusual but predictable problems such as running out of resources (memory or disk space).
