Introduction to development
Before we can write and execute our first program, we need
to understand in more detail how programs get developed. Here is a graphic
outlining a simplistic approach:
Step 1: Define the problem that you would like to solve.
This is the “what” step, where you figure out what you are going to solve.
Coming up with the initial idea for what you would like to program can be the
easiest step, or the hardest. But conceptually, it is the simplest. All you
need is a an idea that can be well defined, and you’re ready for the next step.
Step 2: Determine how you are going to solve the problem.
This is the “how” step, where you determine how you are going to solve the
problem you came up with in step 1. It is also the step that is most neglected
in software development. The crux of the issue is that there are many ways to
solve a problem — however, some of these solutions are good and some of them
are bad. Too often, a programmer will get an idea, sit down, and immediately
start coding a solution. This almost always generates a solution that falls
into the bad category.
Typically, good solutions have the following characteristics:
* They are straightforward
* They are well documented
* They can be easily extended (to add new features that were not originally
anticipated)
* They are modularized
The problem is largely with the third and fourth bullets — while it’s
possible to generate programs that are straightforward and well documented
without using a lot of forethought, designing software that is extensible and
sufficiently modularized can be a much tougher challenge.
As far as extensibility goes, when you sit down and start coding right away,
you’re typically thinking “I want to do _this_”, and you never consider that
tomorrow you might want to do _that_. Studies have shown that only 20% of a
programmers time is actually spent writing the initial program. The other 80%
is spent debugging (fixing errors) or maintaining (adding features to) a
program. Consequently, it’s worth your time to spend a little extra time up
front before you start coding thinking about the best way to tackle a problem,
and how you might plan for the future, in order to save yourself a lot of time
and trouble down the road.
Modularization helps keep code understandable and reusable. Code that is not
properly modularized is much harder to debug and maintain, and also harder to
extend later. We will talk more about modularization in the future.
Step 3: Write the program
In order the write the program, we need two things: First we need knowledge
of a programming language — that’s what these tutorials are for! Second, we
need an editor. It’s possible to write a program using any editor you want, be
it Window’s notepad or Linux’s gedit. However, we strongly urge you to use an
editor that is designed for coding.
A typical editor designed for coding has a few features that make
programming much easier, including:
1) Line numbering. Line numbering is useful when the compiler gives us an
error. A typical compiler error will state “error, line 64″. Without an editor
that shows line numbers, finding line 64 can be a real hassle.
2) Syntax highlighting and coloring. Syntax highlighting and coloring
changes the color of various parts of your program to make it easier to see the
overall structure of your program.
3) An unambiguous font. Non-programming fonts often
make it hard to distinguish between the number 0 and the letter O, or between
the number 1, the letter l (lower case L), and the letter I (upper case i). A good programming font will differentiate these
symbols in order to ensure one isn’t accidentally used in place of the other.
Your C++ programs should be called
name.cpp, where
name is
replaced with the name of your program. The .cpp extension tells the compiler
(and you) that this is a C++ source code file that contains C++ instructions.
Note that some people use the extension .cc instead of .cpp, but we recommend
you use .cpp.
Also note that many complex C++ programs have multiple .cpp files. Although
most of the programs you will be creating initially will only have a single
.cpp file, it is possible to write single programs that have tens if not
hundreds of individual .cpp files.
Step 4: Compiling
In order to compile a program, we need a
compiler. The job
of the compiler is twofold:
1) To check your program and make sure it follows the syntactical rules of the
C++ language:
2) To take your source code as input and produce a machine language
object
file as output. Object files are typically named
name.o or
name.obj,
where
name is the same name as the .cpp file it was produced from. If
your program had 5 .cpp files, the compiler would generate 5 object files.
For illustrative purposes only, most Linux and Mac OS X systems come with a
C++ compiler called g++. To use g++ to compile a file from the command line, we
would do this:
"g++" -c file1.cpp file2.cpp
file3.cpp *
This would create file1.o, file2.o, and file3.o. The -c means “compile
only”, which tells g++ to just produce .o files.
Other compilers are available for Linux, Windows, and just about every other
system. We will discuss installing a compiler in the next section, so there is
no need to do so now.
For complex projects, some development environments use a
makefile,
which is a file that tells the compiler which files to compile. Makefiles are
an advanced topic, and entire books have been written about them. We will not
discuss them here.
Step 5: Linking
Linking is the process of taking all the object files for a program and
combining them into a single executable.
In addition to the object files for a program, the linker includes files
from the runtime support library. The C++ language itself is fairly small and
simple. However, it comes with a large library of optional components that may
be utilized by your program, and these components live in the runtime support
library. For example, if you wanted to output something to the screen, your
program would include a special command to tell the compiler that you wanted to
use the I/O (input/output) routines from the runtime support library.
Once the linker is finished linking all the object files (assuming all goes
well), you will have an executable file.
Again, for illustrative purposes, to link the .o files we created above on a
Linux or OS X machine, we can again use g++:
g++ -o prog file1.o file2.o file3.o
The -o tells g++ that we want an executable file named “prog” that is built
from file1.o, file2.o, and file3.o
The compile and link steps can be combined together if desired:
g++ -o prog file1.cpp file2.cpp
file3.cpp
Which will combine the compile and link steps together and directly produce
an executable file named “prog”.
Step 6: Testing and Debugging
This is the fun part (hopefully)! You are able to run your executable and
see whether it produces the output you were expecting. If not, then it’s time
for some debugging. We will discuss debugging in more detail soon.
Note that steps 3, 4, 5, and 6 all involve software. While you can use
separate programs for each of these functions, a software package known as an
integrated
development environment (IDE) bundles and integrates all of these
features together. With a typical IDE, you get a code editor that does line
numbering and syntax highlighting. The IDE will automatically generate the
parameters necessary to compile and link your program into an executable, even
if it includes multiple files. And when you need to debug your program, you can
use the integrated debugger. Furthermore, IDE’s typically bundle a number of
other helpful editing features, such as integrated help, name completion, a
class hierarchy browser, and sometimes a version control system.
Hope This is clear enought as an introduction to development
Note : That this isn't written by me I found it on google but soon I will post my E-book So keep hanging arround
Thanks for reading
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