CISC/CMPE320
• Reminders:
• Course Web Site:
http://research.cs.queensu.ca/home/cisc320
• Have you filled out the questionnaire in Moodle?
(39 left – as of last night).
• Are you able to run a C++ console program in
your IDE of choice?
• Today:
– “Hello World” Ritual
– Some history of C++
Fall 2015
CISC/CMPE320 - Prof. McLeod
1
Demo - “Hello World” in C++
• For simple console demos I’m going to use the
Eclipse CDT.
• A few notes:
– Make sure your project has the proper “Includes” links.
– You should provide the extension “.cpp” for a source
code file, or “.h” for a header, or declaration file.
– Suggest that you turn off automatic building. (Off by
default…)
– But, don’t forget to save, then build before you run.
Fall 2015
CISC/CMPE320 - Prof. McLeod
2
Some Explanation
• #include is a preprocessor directive that is used
to include external code into your program.
• iostream is a library of I/O streams (makes
sense!).
• A namespace is a collection of name definitions.
(The same name can be used in separate
namespaces). using namespace std; says that
your program is using names from the std (or
“standard”) namespace.
• Another way to do this is to use the :: “scope
resolution operator”, as in std::cout (but this gets
to be a pain of youCISC/CMPE320
are using
a lot of names…)
Fall 2015
- Prof. McLeod
3
Some Explanation, Cont.
• int main() is a function header.
• Code within the function is contained between {
}
• cout is an object from the iostream library that
represents the console output stream.
• << is the “insertion operator” and is used to insert
the supplied string literal into the cout object.
• endl stands in for a line feed character.
• In ISO C++ the return 0; is supposed to be
optional, but some older compilers still require it.
Fall 2015
CISC/CMPE320 - Prof. McLeod
4
Some More Explanation…
• Note that older style C libraries still use the “.h”
extension, as in stdio.h.
• The newer library uses cstdio instead.
• Sometimes you just don’t know, so you have to
experiment. For example, from the STL, you
could try:
– Vector
– vector.h
– vector
• One of them should work!
• I will always try to use the latest library names.
Fall 2015
CISC/CMPE320 - Prof. McLeod
5
Aside:How to Run C++11 Code in Eclipse
• Assuming the MinGW (or GCC) compiler.
• To change for just a project:
• C/C++ Build -> Settings -> Tool Settings -> GCC
C++ Compiler -> Miscellaneous -> Other Flags.
Put “-std=c++11” at the end (after a space).
• Click on “Apply” after the change.
Fall 2015
CISC/CMPE320 - Prof. McLeod
6
History of C++
In the beginning there was C…
Not really, but let’s not go back too far…
Fall 2015
CISC/CMPE320 - Prof. McLeod
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History of C++ - BCPL
• 1966 is before you were born, so let’s start there:
• BCPL or “Basic Computer Programming
Language” designed by Martin Richards of the
University of Cambridge.
• Used to write compilers.
• It was the first language that created “O-code”
before executable code:
Fall 2015
CISC/CMPE320 - Prof. McLeod
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Aside – “O-Code”
BCPL
Java
Source Code
Source Code
Compiler
O-Code
Virtual Machine
Compiler
Generic
Hardware
Dependent
Byte Code
JVM
Machine Code
Machine Code
CPU
CPU
Fall 2015
CISC/CMPE320 - Prof. McLeod
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“O-Code”, Cont.
• Before BCPL, when they wanted to run on a new
platform, the entire compiler program had to be
re-written (took 5 man-months…).
• Now only the part (about 1/5 of the total code) that
generated the machine code – the “Virtual
Machine” had to be changed, the part that
generated the generic O-Code did not have to
change.
• Radical Idea!
• (Also the first language to use { } and // for
comments.)
Fall 2015
CISC/CMPE320 - Prof. McLeod
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B
• Written at Bell Labs by Ken Thompson with
contributions by Dennis Ritchie. First appeared in
1969.
• Stripped down version of BCPL to run on
“minicomputers” like the DEC PDP-11.
• Had a single data type, the “word” that was an
integer most of the time, but could also be a
memory reference.
• Gradually evolved into C in the early 70’s.
Fall 2015
CISC/CMPE320 - Prof. McLeod
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• Ken Thompson
(seated) and Dennis
Ritchie working on a
DEC PDP11 in 1970:
• They also invented the
UNIX OS.
• (The PDP11 was a 16
bit machine.)
Fall 2015
CISC/CMPE320 - Prof. McLeod
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C
• Dennis Ritchie, of Bell Labs, is given credit for C
in 1972.
• A procedural language used for systems
programming (compilers for example) and for
embedded systems.
• Gives low level access to memory and efficient
translation to machine code.
• No longer have to code in Assembly language!
• Used on any kind of computer during the late 70’s
and early 80’s including the IBM-PC.
• In 1983 the language was standardized by ANSI,
giving birth to “ANSI C”, also called “C89”.
Fall 2015
CISC/CMPE320 - Prof. McLeod
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C With Classes
• Was developed by Bjarne Stroustrup at Bell Labs
starting in 1979, as an enhancement to C.
• Added to C:
–
–
–
–
–
–
classes
virtual functions
operator overloading
multiple inheritance
templates
exception handling, etc.
• In 1983 the name of the language was changed to
C++ (the increment operator…).
Fall 2015
CISC/CMPE320 - Prof. McLeod
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C++ Standards
• It took a long time, but the language was first
standardized in 1998 by ISO.
• The standard was updated in 2003 and amended
in 2005 (310 pages, without the library!).
• Another standard was completed in 2011:
“C++11” (August 12, 2011, 1338 pages!).
• C++14 came out on August 18, 2014. A smaller
set of changes from C++11.
• Work is underway on C++17.
Fall 2015
CISC/CMPE320 - Prof. McLeod
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C++ Standards, Cont.
• But:
• It takes a while (and a considerable amount of
work) to update compilers to the new standards.
• See:
http://en.cppreference.com/w/cpp/compiler_support
for a summary of how various compilers are doing.
• GCC version 4.8.1 is now up-to-date with C++11.
• Visual Studio is almost as good and Clang is also
up-to-date with C++11.
Fall 2015
CISC/CMPE320 - Prof. McLeod
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C++ Standards, Cont.
• Compilation is *not* standardized, just the syntax.
• How does Java compare, for example?
Fall 2015
CISC/CMPE320 - Prof. McLeod
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The “Philosophy” of C++
• From “The Design and Evolution of C++” by (who
else!) Bjarne Stroustrup, 1994:
• C++ is designed to be a statically typed, generalpurpose language that is as efficient and portable
as C.
• C++ is designed to directly and comprehensively
support multiple programming styles (procedural
programming, data abstraction, object-oriented
programming, and generic programming).
• C++ is designed to give the programmer choice,
even if this makes it possible for the programmer
to choose incorrectly.
Fall 2015
CISC/CMPE320 - Prof. McLeod
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The “Philosophy” of C++, Cont.
• C++ is designed to be as compatible with C as
possible, therefore providing a smooth transition
from C.
• C++ avoids features that are platform specific or
not general purpose.
• C++ does not incur overhead for features that are
not used (the "zero-overhead principle").
• C++ is designed to function without a
sophisticated programming environment.
Fall 2015
CISC/CMPE320 - Prof. McLeod
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ISO C++ and C
• The C++ standard library has incorporated the
standard C library with just a few optimizations.
• C++ also has the “Standard Template Library”, or
“STL”, that contains many pre-defined data
structures, for example.
• Generally, well-written C code will run in C++.
• But some C “things” will not work in C++ (for
example, in C you can use new or class as
variable names, since they are not C keywords.)
Fall 2015
CISC/CMPE320 - Prof. McLeod
20
Running a C++ Program
Source Code, *.cpp, *.h
Source Code
Editor
Compiler
Library Code
O-Code, *.o
Linker
Machine Code, *.exe
CPU
Fall 2015
CISC/CMPE320 - Prof. McLeod
21
Running a C++ Program, Cont.
• Thankfully, an IDE simplifies this process for you.
• A project (a set of source code and resource files)
is “built” – which consists of both compilation and
linking.
• MinGW (“Minimalist GNU for Windows”), for
example uses the g++.exe program for this. The
IDE makes up the command line calls to this
program.
• Building creates a *.o file and then a *.exe file.
• Then you run the *.exe program.
• Each stage of this process can unearth errors.
Fall 2015
CISC/CMPE320 - Prof. McLeod
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Who Reports the Errors?
• An Eclipse pre-compiler does a pretty good job of
reporting syntax errors and warnings. Errors may
prevent building. You can (but should not!) ignore
warnings.
• Build errors are reported by the compiler and are
seen in the console window.
• Run-time errors are reported by the OS, which is
running the *.exe file.
Fall 2015
CISC/CMPE320 - Prof. McLeod
23
Variable Types
• How many variable types do you have in C? (not
counting structs)?
• You can have the atomic types, pointers and
arrays of these types. Anything else?
•
•
•
•
•
How many types can you have in C++?
Infinitely many!
Thousands defined in the STL.
You can define as many as you want.
Oh – the atomic types are still there too…
Fall 2015
CISC/CMPE320 - Prof. McLeod
24
Variable Declaration
• C++ is declarative and statically typed.
• ie. “Declare before you use” and “You can’t
change the type of a variable, once declared”.
• Unlike C, you can declare variables anywhere, as
long as you satisfy the above.
• Initialization is good practice, but is optional.
• Examples:
int numStudents(40); // C++ style declare
bool flagVal(true);
double aNum;
Fall 2015
CISC/CMPE320 - Prof. McLeod
25
Variable Declaration, Cont.
• This is what we are used to from Java:
int numStudents = 40;
bool flagVal = true;
• For a C++ “style” declaration, use:
int numStudents(40);
bool flagVal(true);
• Looks like you are invoking a constructor doesn’t
it?
Fall 2015
CISC/CMPE320 - Prof. McLeod
26
Type Categories in C++
• Fundamental types:
– bool, char, integer types and floating point types
•
•
•
•
•
•
Enumerated types.
The void type.
Pointer types (like int*)
Array types (like int[])
Reference types (like int&)
Data structures (like vector) and classes
Fall 2015
CISC/CMPE320 - Prof. McLeod
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bool and char Types
• bool literal values: true and false
• char literal values: 'H'
• Escape characters:
–
–
–
–
–
–
–
–
–
–
–
Fall 2015
\n
\t
\b
\r
\a
\?
\\
\'
\"
\0##
\x##
newline
tab
backspace
carriage return
BEL
?
\
'
"
octal
hex
CISC/CMPE320 - Prof. McLeod
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Integer Types
• Simplify things a bit (forget unsigned…):
–
–
–
–
short
int
long
long long
2 bytes
4 bytes
4 bytes
8 bytes
• To get a long long literal append an l or better
yet, an L to the end of the number.
• What is “unsigned” anyways?
Fall 2015
CISC/CMPE320 - Prof. McLeod
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Floating Point Types
• float
• double
• long double
4 bytes
8 bytes
12 bytes
• Literal floating point numbers have a decimal
place and/or an exponent: 4.5, 2.3e-7, for
example.
• A float literal has an f or F appended to it.
• A long double gives you easy access to
extended precision numbers.
Fall 2015
CISC/CMPE320 - Prof. McLeod
30
TestTypes Demo
• Your compiler will determine the amount of
memory allocated to the numeric types.
• Use the sizeof() function to find out.
• Do integers wrap around as they do in Java?
• See the demo…
• Note that there is some variation on these types
depending on the compiler you are using.
Fall 2015
CISC/CMPE320 - Prof. McLeod
31
Aside - Divide by Zero Example
• How does Eclipse/GCC handle a divide by zero?
• Check out TestZeroDivide.cpp.
• Note: compilation errors and warnings, run-time
errors. Note that the run-time error results from
the crashing of the executable, and is reported by
the OS, not Eclipse.
• How does Java handle a divide by zero?
Fall 2015
CISC/CMPE320 - Prof. McLeod
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