Transcript Programming Languages

Chapter 9
Programming
Languages
©Brooks/Cole, 2003
OBJECTIVES
After reading this chapter, the reader should
be able to:
Have a vision of computer language evolution.
Distinguish between machine, assembly, and highlevel languages.
Understand the process of creating and running a
program.
Distinguish between the different categories of
languages: procedural, object-oriented, functional,
declarative, and special.
Become familiar with elements of the procedural
language C.
9.1
EVOLUTION
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Figure 9-1
Evolution of computer languages
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Program 9.1
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Program in machine language
00000000
00000100
0000000000000000
01011110 00001100110000100000000000000010
11101111 000101100000000000000101
11101111 10011110 0000000000001011
11111000 10101101
11011111 0000000000010010
0110001011011111 0000000000010101
11101111 00000010
11111011 0000000000010111
11110100 1010110111011111 0000000000011110
0000001110100010
11011111 0000000000100001
11101111 00000010
11111011 0000000000100100
01111110 11110100 10101101
11111000 10101110 110001010000000000101011
0000011010100010
11111011 0000000000110001
11101111 00000010
11111011 0000000000110100
00000100
0000000000111101
00000100
0000000000111101
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Note:
The only language understood by
a computer is machine language.
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Program 9.2 Program in symbolic language
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Entry
subl2
jsb
movab
main, ^m<r2>
#12,sp
C$MAIN_ARGS
$CHAR_STRING_CON
pushal
pushal
calls
pushal
pushal
calls
mull3
pushal
calls
clrl
ret
-8(fp)
(r2)
#2,read
-12(fp)
3(r2)
#2,read
-8(fp),-12(fp),6(r2)
#2,print
r0
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Symbolic languages
► Assembly
language is a symbolic language.
► An assembler is used to translate symbolic
code into machine language.
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Program 9.3
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/*
Program in C++ language
This program reads two integer numbers from the
keyboard and prints their product.
*/
#include <iostream.h>
int main (void)
{
// Local Declarations
int number1;
int number2;
int result;
//
Statements
cin >> number1;
cin >> number2;
result = number1 * number2;
cout << result;
return 0;
}
// main
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9.2
BUILDING
A
PROGRAM
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Figure 9-2
Building a program
Building a program
► Three
steps to building a program:
 Writing an editing the program
►Using
text editor to edit the source file
 Compiling the program
►Two
programs: the preprocessor and the translator
 Linking the program with the required library
modules
►The
linker assembles all of the subprograms into the
final executable program
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9.3
PROGRAM
EXECUTION
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Figure 9-3
Program execution
disk
computer
monitor
9.4
CATEGORIES
OF
LANGUAGES
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Figure 9-4
Categories of languages
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Procedural language
►A
procedural (imperative 命令) language is
a set of instructions that are executed one
by one from beginning to end unless an
instruction forces the control elsewhere.





FORTRAN
COBOL
Pascal
C
Ada
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FORTRAN
► FORTRAN:
FORmula TRANslation
 Designed by a group of IBM engineers (1957)
 The first high-level language
 Features:
►High-precision
arithmetic (高精確度的計算)
►Capability of handling complex numbers (複數)
►Exponentiation computation (ab) (指數)
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COBOL
► COBOL: COmmon Business-Oriented language
 Designed by Grace Hopper group
 A business programming language
 Features:
►Fast
access to files and databases
►Fast updating of files and databases
►Large amounts of generated reports
►User-friendly formatted output
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Pascal
► Pascal
 Invented by Niklaus Wirth (1971)
 Pascal was designed --►To
teach programming to novices by emphasizing the
structured programming approach
 Pascal became the most popular language in
academic (學術界)
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C
►C
 Developed by Dennis Ritchie at Bell Laboratories (1970s)
 Most of the UNIX operating system is written in C
 Features:
►C has all the high-level instructions
►C has some low-level instructions
►C is a very efficient language; its instructions are
short
►C has been standardized by ANSI (專門認定語言標準
的機構) and ISO
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Ada
► Ada:
 Created for the U.S. Department of Defense
(DoD 美國國防部)
 Features:
►Ada
has high-level instructions.
►Ada has instructions to allow real-time processing.
This make it suitable for process control.
►Ada has parallel-processing capabilities. It can run on
mainframe computers with multiple processors.
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Object-Oriented languages
► In
object-oriented programming, the objects
and the operations to be applied to them
are tied together.
► The objects in object-oriented programming
are active.
 C++
 Java
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C++
► C++: developed by Bjarne Stroustrup at Bell Lab
► Three
principles:
 Encapsulation (封裝)
►The user knows what to do with the data without
knowing how it is done.
 Inheritance (繼承)
►When a general class is defined, you can define a
more specific class that inherits some of the
characteristics of the general class but also has some
new characteristics.
 Polymorphism (多型)
►You can define several operations with the same
name that can do different things in related classes.
Java
► Java:
Developed at Sun Microsystems,, Inc.
The language is totally class oriented.
Every data item belongs to a class.
The browser can download the applet (小小的應
用程式) and run it locally.
 Features:
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
►Class
library
►Multithreading
©Brooks/Cole, 2003
Figure 9-5
Functional languages
►A
functional language:
 Predefines a set of primitive functions
 Allow the programmer to combine primitive
functions to create new function
Function in a functional language
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Figure 9-6
Extracting the third element of a list
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Functional languages
► Advantages:
 Encourage modular programming
 Allow the programmer to make new functions
out of existing ones
► Examples:
 LISP: designed at MIT
 Scheme: LISP similar
©Brooks/Cole, 2003
Scheme
► For
example:
 car : extract the first element of a list
 cdr : extracts the rest of the elements in a list
except the first one
(car 2 3 7 8 11 17 20)  2
(cdr 2 3 7 8 11 17 20)  3 7 8 11 17 20
(car (cdr (cdr 2 3 7 8 11 17 20)))  7
©Brooks/Cole, 2003
Declarative language
►A
declarative language uses the principle of
logical reasoning to answer queries.
► Logical
reasoning is based on deduction (歸納).
► For example:
If (A is B) and (B is C), then (A is C)
► Problem:
 Collecting all the facts into one program make the
program huge.
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Prolog
► Prolog:
 Developed by A. Colmerauer in France in 1972.
 A program in Prolog is made of facts and rules.
 Example:
human ( John )
mortal ( human ) (註：mortal難免一死的)
?-mortal ( John ) (註：user ask)
yes (註：program answer)
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Special languages
► HTML
(Hypertext Markup Language)
 An HTML file is stored on the server and can be
downloaded by a browser.
 The instructions are stored with the text.
 Any browser can read the instructions and
format the text according to the workstation
being used.
 HTML lets you use only ASCII characters for
both the main text and formatting instructions.
 Head, Body, and Tags
©Brooks/Cole, 2003
Table 9.1 Common tags
Beginning Tag
---------------<HTML>
<HEAD>
<BODY>
<TITLE>
<Hi>
<B>
<I>
<U>
<SUB>
<SUP>
<CENTER>
<BR>
<OL>
<UL>
<LI>
<IMG>
<A>
Ending Tag
---------------</HTML>
</HEAD>
</BODY>
</TITLE>
</Hi>
</B>
</I>
</U>
</SUB>
</SUP>
</CENTER>
</OL>
</UL>
</LI>
</A>
Meaning
---------------------------document
document head
document body
document title
different header levels
boldface
Italic
underlined
subscript
superscript
centered
line break
ordered list
unordered list
an item in the list
an image
an address (hyperlink)
Program 9.4
HTML Program
<HTML>
<HEAD>
<TITLE> Sample Document </TITLE>
</HEAD>
<BODY>
This is the picture of a book:
<IMG SRC="Pictures/book1.gif" ALIGN=MIDDLE>
</BODY>
</HTML>
©Brooks/Cole, 2003
Special languages
► PERL (Practical Extraction and Report Language)
 A high-level language with a syntax similar to
the C but more efficient
 The power of PERL lies in its well-designed use
of regular expressions.
► SQL
(Structured query Language)
 A language used to answer queries about
databases.
 See Chapter 14.
©Brooks/Cole, 2003
9.5
A PROCEDURAL
LANGUAGE:
C
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C — Identifiers
► Identifiers
(識別字)
 Identifiers allow you to name data and other
objects in the program
 Different programming languages use different
rules for form identifiers
 The first character of the identifier cannot be a
digit.
 Reserved words (key words): about 50 words.
©Brooks/Cole, 2003
C — Data types
► Data
types
 A data type defines a set of values and a set of
operations that can be applied to those values.
 Standard types:
►
integer, char, float
 Derived (衍生的) types:
►pointer,
enumerated type, union, array, and structure.
©Brooks/Cole, 2003
Figure 9-7
C — Variables
► Variables
are names for memory location.
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Variables
► Declaration
(宣告)
 A declaration is used to name a variable.
► Definitions
 Definitions are used to create the variable and to
allocate a memory location for it.
 Example: float price;
► Initialization
 The initializer establishes the first value that the variable
will contain.
 Example: float price = 23.45;
©Brooks/Cole, 2003
C — Constants
► Constants
are data values that cannot be
changed during the execution of a program.
► Three types:
 Literal constant
circumference = 2 * length * width ;
 Named constant
const pi = 3.14;
 Symbolic constant
#define taxRate 0.0825
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C — Input and output
► Input
 Example: scanf (“%d”, &num);
► Output
 Example:
printf (“The value of the number is: %d” , num);
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C — Expressions
► An
expression is a sequence of operands and
operators that reduces to a single value.
 Example: 2 * 5
► Operators
 An operator is a language-specific syntactical token that
requires an action to be taken.
► Operand
 A operand receives an operator’s action.
 The operands of multiply are the multiplier and the
multiplicand.
©Brooks/Cole, 2003
Arithmetic operators
Operator
---------------+
*
/
%
---------++
--
Definition
---------------Addition
Subtraction
Multiplication
Division (quotient)
Division (remainder)
----------------------Increment
Decrement
Example
---------------------3 + 5
2 - 4
Num * 5
Sum / Count
Count % 4
----------------------Count ++
Count --
Table 9.2 Arithmetic operators
©Brooks/Cole, 2003
Relational operators
Operator
---------------<
<=
>
>=
==
!=
Definition
---------------Less than
Less than or equal to
Greater than
Greater than or equal to
Equal to
Not equal to
Example
---------------------Num1 < 5
Num1 <= 5
Num2 > 3
Num2 >= 3
Num1 == Num2
Num1 != Num2
Table 9.3 Relational operators
©Brooks/Cole, 2003
Logical operators
Operator
---------------!
&&
||
Definition
---------------NOT
AND
OR
Example
---------------------! ( Num1 < Num2 )
(Num1 < 5 ) && (Num2 > 10 )
(Num1 < 5 ) || (Num2 > 10 )
Table 9.4 Logical operators
©Brooks/Cole, 2003
Assignment operators
Operator
---------------==
+=
-=
*=
/=
%=
Example
---------------Num
=5
Num += 5
Num -= 5
Num *= 5
Num /= 5
Num %= 5
Meaning
---------------------Store 5 in Num
Num = Num + 5
Num = Num - 5
Num = Num * 5
Num = Num / 5
Num = Num % 5
Table 9.5 Assignment operators
©Brooks/Cole, 2003
Figure 9-8
Statements
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C — Statements
► Expression
statements
a++;
b = 4;
c = b + c * 4;
► Compound
statements
{ x = 1; y = 20 ; }
©Brooks/Cole, 2003
C — Functions
► In
C, a subroutine is called a function.
► A function’s side effect is an action that
results in a change in the state of the
program. The side effect can involve - Accepting data from outside the program
 Sending data out of the program to the monitor
or a file
 Changing the value of a variable in the calling
function
©Brooks/Cole, 2003
Figure 9-9
Side effect of a function
©Brooks/Cole, 2003
Figure 9-10
Function declaration
Parameter passing
► Pass
by value
 When you pass by value, a copy of the data is
created and placed in a local variable in the
called function.
 The original data in the calling function are safe
and unchanged.
► Pass
by reference
 Pass by reference send the address of a variable
to the called function.
 When you want to change the contents in a
variable in the calling function, you must pass
by reference.
Figure 9-11
Selection
if-else statement
©Brooks/Cole, 2003
Figure 9-12
switch
statement
©Brooks/Cole, 2003
Figure 9-13
Repetition
while
loop:
a pretest
loop
Figure 9-14
for loop:
a pretest
loop
Figure 9-15
do-while
loop:
a posttest
loop
Key terms
Ada
Arithmetic operator
► Assembler
► Assembly language
► Assignment operator
► C
► C++
► Class
► COBOL
► Compiler
► Compound statement
► Computer language
► Constant
►
►
Data type
Declaration
► Declarative language
► Definition
► Derived types
► Executable file
► Expression
► Expression statement
► FORTAN
► Function
► Functional language
► High-level language
► HTML
►
►
©Brooks/Cole, 2003
Identifier
► Imperative language
► Inheritance
► Java
► Keyword
► Linker
► LISP
► Loader
► Logical operator
► Machine language
► Natural language
► Object-oriented language
► Operand
► Operation
► Operator
► Pascal
►
Pass by reference
► Pass by value
► PERL
► Processor
► Procedural language
► Programming language
► Prolog
► Relational operator
► Reserved word
► Scheme
► Side effect
► Source file
► SQL
► Symbolic language
► Text editor
► variable
►
©Brooks/Cole, 2003