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CSC240 :: Lecture Note :: Week 01
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Overview

Assignment(s): #email (due 9/8/2017) and #bwk (due 9/112017) and #MakeHelloWorld (due 9/15/2017)

Handouts: Syllabus | AboutCSC240 | HowToSubmitAssignments

Code: helloworld.c | HelloWorld.cpp | HelloWorld2.cpp | { preproc.cpp | preproc0.h | preproc1.h }
C++Template.txt | BadHelloWorld.cpp | LongStringLiteral.cpp


Syllabus Review

It is the student's responsibility to read and understand the syllabus.

The following are a small number of "tips for success."

CSC240 Syllabus

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FooBits

It's possible "program or be programmed" is true.

   "If you're joining the company in your 20s, unlike when I joined, 
    you're going to learn to code. It doesn't matter if you're in 
    sales, finance, or operations. You may not end up a programmer, 
    but you will know how to code." -- Jeff Immelt, GE chairman/CEO 

Spectrum.IEEE.org::The 2017 Top Programming Languages

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Course Resources/Tools

Books

C++: SEAS.Harvard.edu::Thinking in C++ by Bruce Eckel

Lisp: CS.CMU.edu::COMMON LISP: A Gentle Introduction to Symbolic Computation by David S. Touretzky
Lisp: GigaMonkeys.com::Practical Common Lisp by Peter Seibel
Lisp: CS.CMU.edu::Common Lisp the Language, 2nd Edition
Lisp: cl-cookbook.sourceforge.net::The Common Lisp Cookbook
Lisp: LispWorks.com::Common Lisp HyperSpec

Prolog: LearnPrologNow.org::Learn Prolog Now!
Prolog: CDN.preterhuman.net::The Art of Prolog by Leon Sterling and Ehud Shapiro
Prolog: gprolog.org::manual::GNU Prolog (gprolog001)

Tutorials

C++: CPlusPlus.com | TutorialsPoint.com

Lisp: TutorialsPoint.com
Lisp: PaulGraham.com::lisp.html
Lisp: CS.sfu.ca::Learning Lisp for CMPT 310

Prolog: LearnPrologNow.org
Prolog: NewThinkTank.com::Learn Prolog In One Video
Prolog: Prolog-Heritage.org::Prolog Heritage

CodingGround

TutorialsPoint.com::CodingGround::C++ | Lisp | Prolog

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hello, world


The C and C++ Compilation Process

C and C++ are high-level, 3rd-generation languages. These types of languages must be translated into a machine language in order to be executed by a CPU. The process of translating high-level language into machine language is called the compilation process.

The compilation process consists of the following steps.

   edit source code ->  compile   ->   link    ->   execute
      (editor)         (compiler)    (linker)       (loader)

Program source code is entered into a file using a text editor. After the code has been entered, a compiler program is started that translates the source into an object code file. The object code file is linked with other object code files that come with the compiler and an executable file (or program) is created. In order to execute the program, a program called the loader copies the executable file into the memory of the computer and sends an execute command to the CPU.

It should be noted that errors can occur during each step


source      +----------+      object     +--------+      executable
file   ---> | compiler | ---> file  ---> | linker | ---> file      ---+
(x.c)       +----------+      (x.o)      +--------+      (x)          |
                                             ^                        |
                                             |                        v
                                             |                    +--------+
                                             |                    | loader |
                                     Standard C Library           +--------+
                                     (stdc.lib                        |
                                          stdio.o                     |
                                          stdlib.o                    v
                                          math.o                     CPU
                                          ...)

A source file ending with ".c" contains C source code; whereas, a file ending with ".cpp" is a C++ file (note: ".C" suffix may also indicate a C++ source file). A file ending with ".h" can be both a C and C++ header file. Sometimes the suffix ".hpp" (or ".H") is used to indicate a C++ only header file.

The compiler is a program that usually consists of many phases. The first phase of compilation is called preprocessing. The preprocessor does many things, but two features that must be learned immediately are file inclusion and macro (manifest constant) definitions. After preprocessing, the compiler executes two primary steps: lexical analysis and parsing. During lexical analysis, the source code is broken up into tokens and the tokens are passed to the parser. The parser does syntax and semantic analysis, which includes the generation of object code (i.e. machine language).

The linker "combines" all object code files into an executable file (by default, named a.out on Unix systems). Typically, the object files created by your source files are linked with object files that are packaged into libraries.

Most implementations allow each step of the compilation process to be executed as a stand-alone procedure. For example, compile a source file but do not invoke the linker; execute the preprocessor only; or, invoke the linker only.

Some older compilers translate C source code into assembly language, then execute an assembler program to translate the assembly language into machine language.

Early C++ compilers (those prior to 1992) translated C++ code into C code and then executed the C compiler.

The loader reads a program (i.e. executable file) into memory. Once this is completed, it becomes a process and the CPU executes it.

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Variables, Identifiers and Keywords

A variable is a location in the computer's memory where a value can be stored for use by a program.

An identifier is a name supplied to a variable. An identifier in C is a sequence of letters and digits. The first character must be a letter; the underscore _ counts as a letter. Upper and lower case letters are different (i.e. C is case sensitive). Good programming practice: avoid using leading underscores in identifiers. In addition, current convention is to start variable names with a lower case letter.

A keyword is a predefined identifier that has special meaning to the compiler and it is reserved by the language.

C Keywords

C reserves the following identifiers for use as keywords, they cannot be used otherwise.

   auto, break, case, char, const, continue, default, do, double,
   else, enum, extern, float, for, goto, if, int, long, register,
   return, short, signed, sizeof, static, struct, switch, typedef,
   union, unsigned, void, volatile, while
C9X indicates that bool will become a C keyword.
C++ Keywords

The following are potential C identifiers that are keywords in C++.

   and, and_eq, asm, bitand, bitor, bool, catch, class, compl, const_cast,
   delete, dynamic_cast, explicit, false, friend, inline, mutable,
   namespace, new, not, not_eq, operator, or, or_eq, private, protected,
   public, reinterpret_cast, static_cast, template, this, throw, true, 
   try, typeid, typename, using, virtual, wchar_t, xor, xor_eq

All of the C keywords are also C++ keywords.

Choosing Identifier Names

Choosing meaningful identifier names helps programs to be "self-documenting."

Generally, 1 or 2 character names are considered cryptic. Some commonly used short names are: c for characters; i, j, k for indexes; n for counters; p or q for pointers; s for strings; and x, y, z for floating-point variables.

Avoid using names that begin with underscores because the implementation may use names like that for its own purposes internally.

Abbreviations for meaningful names, if used, should be used consistently. For example, if nbr is used for number, then always use nbr instead of number.

A name should convey information as to how the variable is used and what type of data it will store. Example: item_cnt, lines_per_pg, max_input, buffer_size, and so on.

Extremely long names can convey lots of information, but they tend to make code difficult to read and maintain. Names should not exceed 31 characters in length.

Some linkers may make as few as the first six characters as significant.

Key Points

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Introduction to the cout Object

In order to use the C++ Streams I/O, the iostream.h header file must be included. In addition, inclusion of iomanip.h is often needed.

   #include <iostream>
   #include <iomanip>

Upon program startup, the cout object of class ostream is instantiated.

Output to the terminal screen (or the standard output) is performed using the cout object, and the left bit-shift operator << in combinations.

   cout << EXPR;
   // in many instances, EXPR needs to be inside ()'s

Multiple values can be output by executing the following.

   cout << EXPR << EXPR << EXPR << ...;

Only one EXPR is allowed after each << The << points in the direction of the data flow to cout (the standard output) and is referred to as the insertion operator.

A cout object does not automatically place spaces between values being output, and it does not automatically add a newline at the end of its output.

Both "\n" and '\n' result in a newline being printed to the standard output. In addition, the endl I/O manipulator can be used to print a newline. Example: the following statements all print a newline followed by the value of an EXPR followed by another newline:

   cout << endl << EXPR << endl;
   cout << "\n" << EXPR << "\n";
   cout << '\n' << EXPR << endl;
   cout << endl << EXPR << "\n";
   cout << '\n' << EXPR << '\n';

C and C++ I/O can be mixed on a per-character basis, but to ensure data is sent/received in the proper order a call to sync_with_stdio() should be made.

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About the cin Object

In order to use the C++ Streams I/O, the iostream.h header file must be included.

Upon program startup, the cin object of class istream is created (instantiated).

Input from the keyboard (or the standard input stream) is performed using the cin object, and the right-shift bit-wise operator >> in combinations such as:

   cin >> someVariable;

Multiple values can be input by executing the following.

   cin >> variable1 >> variable2 >> variable3 >> ...;

Only one variable is allowed after each >>. The >> points in the direction of the data flow from cin (the standard input) and is referred to as the extraction operator.

cin provides support for all of the primitive data types.

cin skips whitespace (where whitespace is defined by a call to isspace() see ctype.h).

   char c;
   cin >> c;  //reads the first non-whitespace character into c

cin.width(int) can be used to restrict the number of characters read (useful when reading strings).

   char a[16];
   cin.width(sizeof(a));
   cin >> a; //read at most 15 characters into a and add terminating null

The input stream has a state associated with it. They are:

Applying an input operation to a string that is not in the good() state is a null operation.

The insertion operator is intended for formatted input; reading objects of an expected type and format. The get() and getline() functions offer alternative ways to get input. These functions treat whitespace characters exactly like other characters.

get() leaves the terminator on the input stream; whereas, getline() doesn't.

   char a[32];
   cin.getline(a, sizeof(a));
      // reads at most 31 characters into array  a
      // appending a null character to the end
      //
      // the standard input stream is read until
      // 31 characters read or a newline is encountered

ignore() reads characters but it doesn't store them anywhere. By default, ignore() reads one character and the terminator is end-of-file.

clear() can be used to clear the input flags.

   int i;
   cout << "Enter an integer: " << flush;
   cin >> i;
   if (cin.fail()) {
      cin.clear();
      cout << "Enter an integer: " << flush;
      cin >> i;
      if (cin.fail())
         cerr << "forget it...";
   }

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About Escape Sequences

Escape sequences are used for the following reasons.

C and C++
  \a  Alert   \b  Backspace   \f  Formfeed
  \n  Newline   \r  Carriage return   \t  Horizontal Tab
  \v  Vertical Tab   \"  Double quote   \'  Single quote
  \\  Backslash   \?  Question Mark   \0  Null Character
There are two types of numeric escape sequences: octal and hexadecimal.
Java Escape Sequences
Java will not compile a source file if it contains invalid escape sequences. [ Example]

  \b  Backspace   \f  Formfeed   \n  Newline
  \r  Carriage return   \t  Horizontal Tab   \"  Double quote
  \'  Single quote   \\  Backslash   \uhhhh  Unicode; 4 hexadecimal digits
  \ooo  C style; 3 octal digits

All of the Java escape sequences -- except for Unicode \u -- can only be used within string and character literals.

   String doubleQuote = "\"";
   char singleQuote = '\'';
   char bestGrade = '\u0041';    // set to 'A'
   char worstGrade = '\106';     // set to 'F'

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Coding and Printing Long String Literals

Printing long string literals (e.g. a multi-line paragraph) posses two programs: keeping the source code nicely formatted, and making sure the program's output is readable (e.g. that the lines are not too long, word breaks are reasonable, and so on).

In general, to keep you code nicely formatted, you need to split your long string literal into multiple string literals and then use one of the following techniques.

The LongStringLiteral.cpp source code example uses all of the aforementioned techniqes.

You cannot press the ENTER key in the middle of a string literal. That results in a compile-time (i.e. syntax) error.

The following technique is an example of using a single cout statement with multiple insertion operators.

   cout << "This is a long string literal that does not fit on"
        << " a single line.  Therefore, I split it into multiple"
        << " string literals.  Unfortuneatly, this string literal"
        << " doesn't contain any newline characters; consequently,"
        << " when it does print, it will not display properly."
        << endl;

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Primitive Data Types

The primitive data types are built-in to the language. They are also referred to as basic, atomic, fundamental, base, and so on.

The C and C++ languages support the following primitive data types.

* The bool primitive data type is in C++ only; however, it has been added to the newest versions of C.

The   char  short   int  long   primitive data types are  integral  data types; whereas,   float  double  long double   are  floating-point  types.

When you define a variable, memory is allocated.

The amount memory allocated is implementation-dependent. For example, on system A an int may take 4 bytes; whereas on system B is takes 2 bytes.

The amount of memory allocated dictates the minimum and maximum values that can be stored in variables.

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Constants

Constants are values that are set at compile-time and cannot be changed at run-time (i.e. they are immutable).

Each constant value is defined to be a specific type.

By default, an integral number is type int. If it is too large (or small) of a value to fit into the size of an int, then it is type long.

By default, a floating-point number is type double.

Character constants are treated as small int values. For example, on some systems, the numeric value of 'A' is 65. The numeric values that are used to represent characters depends on the character set used by the system. [Some popular character sets are ASCII, EBCDIC, and Unicode.

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Arithmetic Operators

All arithmetic operators are binary operators (i.e. they take two operands).

   *     multiply    
   /     divide
   %     modulus (remainder)
   +     addition
   -     substraction

Important points.

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Precedence and Associativity of Operators

Whenever you have an EXPR that contains multiple operators, then you must be aware of operator precedence and associativity.

Precedence and associativity are used to "bind" operators with operands.

Every C/C++ book that I have reviewed contains a precedence and associativity chart. Here is a chart that displays the precedence and associativity of some of the operators we learn first.

Unary + and - have higher precedence than the binary forms.
Operators Associativity
()   +   -   (type)   sizeof right to left
*   /   % left to right
+   - left to right
= right to left

Precedence determines the order in which operands are bound to operators. Operators on the same line have the same precedence; rows are in order of decreasing precedence.

Examples:

If an EXPR contains two operators of equal precedence, then associativity is used to bind operators and operands.

An example using the EXPR:    a + b - c

   The + and - operators have equal precedence; therefore, associativity
   is used.  They associate left-to-right and we end up with with the
   binding  (a + b) - c

Precedence and associativity can be altered by using parenthesis.

   Example expression:  a * b / c

   * and / have equal precedence and they associate left-to-right;
   therefore, we get the following binding:  (a * b) / c  

   If we want the operand  b  to be attached to the operand  c,
   then we would parenthesis and code the EXPR:  a * (b / c).

Use parenthesis if you are ever in doubt about the precedence and associativity rules. [Note: it is possible to overuse ()'s.]

GDT::Resource::C++:: Precedence chart that includes all operators.

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Relational Operators

Relational operators are used to compare the value of two expressions (EXPRs).

 ==   expr1 == expr2 equals
 !=   expr1 != expr2 not equals
 >   expr1 > expr2 greater than
 <   expr1 < expr2 less than
 >=   expr1 >= expr2 greater than or equal to
 <=   expr1 <= expr2 less than or equal to

The operators that are made up of two characters cannot have any whitespace between. For example: = = would be treated as two separate assignment operators and would result in a compile-time error. == is used to test two operands for equality.

It is easy to sometimes use the equality operator in lieu of the assignment operator and vice versa. You must remember the following.

   ==   is the relational equality operator; it compares two operands
        for equality and evaluates to either 0 (false) or 1 (true)

   =    is the assignment operator; it copies the value of the operand
        on the right-hand side to the operand on the left-hand side; the
        EXPR evaluates to the value that was copied (i.e. assigned)

Examples.

   int thisCourse = 100;   /* 100 assigned to thisCourse */
   int nextCourse = 205;   /* 205 assigned to nextCourse */

   thisCourse == nextCourse   /* evaluates to 0 (false) */
   thisCourse != nextCourse   /* evaluates to 1 (true) */
   thisCourse > nextCourse    /* evaluates to 0 */
   thisCourse < nextCourse    /* evaluates to 1 */
   thisCourse >= nextCourse   /* evaluates to 0 */
   thisCourse <= nextCourse   /* evaluates to 1 */

GDT::C++::Code:: RelationalOps.cpp

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