Subsection 1.4.1 Compile-time errors
The compiler can only translate a program if the program is syntactically correct; otherwise, the compilation fails and you will not be able to run your program.
For example, in English, a sentence must begin with a capital letter and end with a period. this sentence contains a syntax error. So does this one
For most readers, a few syntax errors are not a significant problem, which is why we can read the poetry of e e cummings without spewing error messages.
Compilers are not so forgiving. If there is a single syntax error anywhere in your program, the compiler will print an error message and quit, and you will not be able to run your program.
To make matters worse, there are more syntax rules in C++ than there are in English, and the error messages you get from the compiler are often not very helpful. During the first few weeks of your programming career, you will probably spend a lot of time tracking down syntax errors. As you gain experience, though, you will make fewer errors and find them faster.
Subsection 1.4.4 Experimental debugging
One of the most important skills you should acquire from working with this book is debugging. Although it can be frustrating, debugging is one of the most intellectually rich, challenging, and interesting parts of programming.
In some ways debugging is like detective work. You are confronted with clues and you have to infer the processes and events that lead to the results you see.
Debugging is also like an experimental science. Once you have an idea what is going wrong, you modify your program and try again. If your hypothesis was correct, then you can predict the result of the modification, and you take a step closer to a working program. If your hypothesis was wrong, you have to come up with a new one. As Sherlock Holmes pointed out, “When you have eliminated the impossible, whatever remains, however improbable, must be the truth.” (from A. Conan Doyle’s
The Sign of Four).
For some people, programming and debugging are the same thing. That is, programming is the process of gradually debugging a program until it does what you want. The idea is that you should always start with a working program that does
something, and make small modifications, debugging them as you go, so that you always have a working program.
For example, Linux is an operating system that contains thousands of lines of code, but it started out as a simple program Linus Torvalds used to explore the Intel 80386 chip. According to Larry Greenfield, “One of Linus’s earlier projects was a program that would switch between printing AAAA and BBBB. This later evolved to Linux” (from
The Linux Users’ Guide Beta Version 1).
In later chapters I will make more suggestions about debugging and other programming practices.
Checkpoint 1.4.1.
Checkpoint 1.4.2.
Match each term to its definition!
Try again!
- syntax (compile-time) error
- an error that surfaces when something is wrong with the structure of your program
- run-time error
- an error that comes up when your program is executed
- semantic error
- your program does what you told it to do, not what you intended for it to do
Checkpoint 1.4.3.