Transcript CPS120: Introduction to Computer Science

CPS120: Introduction to
Computer Science
Compiling Your First Program
Compilers
An
engine that works on your behalf to process
instructions and allow you to deal with various
basic rules of the language
The
compiler’s job is to make sure you follow the
rules, to require that you provide enough information
that the compiler can translate you instructions into
languages the components can understand
Compilers Available
 Products
range from freeware compilers to work
environments designed for commercial application
development
 Borland
C++ compiler
 CodeWarrior
 IBM Visual Age C++
 Microsoft Visual C++
 GNU freeware
 DJGPP freeware ( www.delorie.com/djgpp/ )
Compilation Process
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2.
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Get the set of instructions from you
Review the instructions to see if they violate the rules
(syntax) of the language
If all the rules are obeyed, create a working file in the
language of the computer (machine language)
Attach to the working file full instructions for any
shortcuts you may have used (linkage)
Assemble a final file in machine language
Compiler Files
Source code
Linked/Library file
Object file
Executable file
Source Code
The set
of instruction that you will develop on
your own for processing by the compiler
Executable Files
A machine-language executable file created
when the compilation process is complete
All
that is needed to run the program
Not human-readable
Has the extension .EXE
Stored in binary form
 Copies
Known
may be distributed (portable)
as an application
Compiling and Debugging
Executable code will
not be created until you
correct all of the syntax errors in your source
code
Then the fun (with logic errors) begins
Creating Source Code Files
Actually Compiling a Program
Creating Source Code
Programmers spend
most of their time with
source code files
Need
to be comfortable with an editor that creates
ASCII text files
 7-bit
Don’t
representation of all keyboard character
use a word processor
If an editor in an environment is available, use that, it
provides more sophisticated tools
Using the Editor
Save often because there is
no autosave in
Visual C++
The editor will do matching of delimiters and
intelligent indentation
C++ Usages & Conventions
 C++
is absolutely case sensitive
 For
Instance: A is 97 in ASCII and a is 65
 Remember: in ASCII {, [, and ( are not equivalent
 No
keywords in ANSI standard are even partially
uppercase
 ‘While’
is not a keyword, ‘while’ is
 Be careful if you define new keywords
 The
most common practice in C+++ is to use small
letters of the first part of a variable name and capitals for
the rest of it
Comments
 Document
what is happening, why it is happening and
other issues
 Commentary is ignored by the compiler
 C++ has inline, block and documentary comments
 Inline
comments are within line of code
 Use
 Block
the // symbols
comments are long comments delimited with /* and */
Scope Delimiters
A symbol or
pair of symbols used to define a
region or area which is considered a locale
In programming, many structures need to have
their scope defined because they should not
affect the entire program
In
C++, the symbols ‘{‘ and ‘}’ are used
Literals
Literals
are system commands and other pieces
of information that the compiler doesn’t
understand, and therefore, takes your word for
them
In C++, literals are enclosed in straight double
quotes " " which is the shift of the apostrophe
Columns and White Space
 Modern
programming languages are free form with
delimiters instead of columns to determine the end of
instructions
 The
; (semi-colon) is the delimiter used in C++
 Use
tabs, indents, and blank lines in any manner that
makes code easier to understand
 Many
programming instructions become subordinate to
other instructions due to scope and other restrictions.
Formatting code to reflect this makes it easier to read
Variables
Variables or
identifiers are used to hold
information
Usually
mixed case with the first letters small and the
rest starting with a capital
e.g. theWeight
Color Coding in Visual C++ Editor
Comments
are green and are ignored by the
compiler
All ANSI keywords are coded in blue
Other code is in plain black
Compiler
in black
keywords like cin and cout are also shown
Setting Up a Visual C++ Workspace
Left-click START
In the program section, select Visual Studio or Visual
C++ (depending on what is installed)
Left click on the Visual C++ icon to load the
environment
Create a new work area by choosing FILE/NEW
Choose FILES tab
Click on the C++ Source File to reach the editor
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2.
3.
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6.
i.
Add a filename and directory before continuing

e.g. c:/cppFun/myFirstCpp
Setting Up a Visual C++ Workspace
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Create the directory with START / EXPLORE
Double-click the drive letter
Choose FILE, NEW FOLDER
Left click on FOLDER
Change new folder to cppFUN
Close Explorer with the X
Back in Visual C++, type myFirstCpp in the file box
Click OK and get back to the main edit screen
Setting Up a Visual C++ Workspace
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16.
Enter the source code
After entering the program, FILE then SAVE
Why Create New Subdirectories?
You
should always use subdirectories to store
your files. Visual C++ creates quire a few work
files when it generates the executable file for you
source code, and they will be easy to dispose of if
you keep everything together in one convenient
place.
Under no circumstances should you use the root
(C:\) directory except on a floppy disk (A:\).
Running the Program
1.
2.
Press the REBUILD ALL button. It has two
arrows in a box
Press the RUN button. It is a red exclamation
point
Disk Space Issues
Text files are
insignificant in terms of space
However, six other files are created every time
something is compiled; some get around 95% full
Highlighting
the disk in are 3 or 4 times larger than
the source
You can delete anything but the file with the .cpp
suffix; everything else can be recreated
Recompiling
1.
2.
3.
4.
Open the file by going the file you stored it in and double
clicking on it
Scan the source code for obvious errors before attempting
to compile
Attempt to compile using the COMPILE button or choosing
the first option on the BUILD menu
Answer Yes to use the default project workspace
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5.
The lower window will be active and the compile will occur
Note the number of errors and warnings
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These need to be dealt with before executable code is created
Working in a Lab Environment
 The
following issues are magnified working in a
laboratory environment:
 Viruses
 Scan
disks transferring between the lab and home
 Plagiarism
 Beware
of shoulder surfing, temp directories, shared directories,
discarded print and new print
 Name things vaguely and delete what you are done with
 Theft
 Take
your floppies and Zip Disks with you
 Malicious
mischief