Download Document

Chapter 9
Programming
Languages
OBJECTIVES
After reading this chapter, the reader should
be able to:
Have a vision of computer language evolution.
Distinguish between machine, assembly, and high-level
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

Computer language –
a set of predefined words that are combined
into a program according to predefined rules
(syntax).
Evolution of computer languages

Each computer has its own machine language,
which is made of streams of 0s and 1s.
Note:
The only language
understood by a computer is
machine language.
Program 9.1
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
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

Symbolic language –
simply mirrored the machine languages using
symbols to represent the various machine
language instructions.

Assembler –
a special program to translate symbolic code
into machine language.
Assembly language

Program 9.2
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Program in symbolic language
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

High-Level language –
 Portable
to many different computers
 Allow programmer to concentrate on application
 Must be converted to machine languages
(Compilation)

Natural language –
English, French, or Chinese
Program 9.3 Program in C++ language
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
/*
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
9.2
BUILDING
A
PROGRAM

Building a program
1.
2.
3.

1.
2.
Writing and Editing
Compiling
Linking
Running
Load
Execute
Building a program
Source file
Object file
Assemble all subprograms into
final executable program
Executable file
9.3
PROGRAM
EXECUTION
Program execution
• Loader –
An OS program to load the program into memory
for executing
9.4
CATEGORIES
OF
LANGUAGES
Categories of languages




Procedural language –
a set of instructions that are executed one by
one from beginning to end unless an instruction
forces the control elsewhere.
When programmers need to solve a problem,
they should know the procedure to follow.
For each problem, the programmer should
carefully design an algorithm, and the algorithm
should be carefully translated to instructions.
Imperative language –
each instruction is a command to the computer
to do some specific task.

Fortran –
 For
scientific and engineering application
 The first high-level language

COBOL –
a

business programming language
Pascal –
 Structured
programming for teaching

C–
 High-level
instructions (Structured programming for
writing UNIX)
 Low-level instructions to access the hardware
directly and quickly.
Closer to assembly language than any other
language.
A good language for system programmers.
 Efficient language; its instructions are short.
 Standardized by ANSI and ISO

Procedural language –
– independent from Operations
 Objects – passive
 Objects

Object-Oriented language –
 An
approach to problem solving that is totally
different from procedural language.
 Objects – tied together with Operations
 Objects – active

C++ 
Developed by Bell Lab.
 adds object-oriented features to its predecessor, C.

Java –

Developed by SUN, Based on C and C++
 Java source code files are compiled into a format called
bytecode , which can then be executed by a Java interpreter.
 Compiled Java code can run on most computers because
Java interpreters and runtime environments, known as Java
Virtual Machines (VMs), exist for most operating systems.
 Programs


Application – a complete stand-alone program that can be run
independently.
Applet – embedded in HTML language, stored on a server, and
run by a client browser.



In Functional language,
a program is considered a mathematical function.
A function is a black box
that maps a list of inputs to a list of outputs.
LISP – designed by MIT
Function in a functional language
Extracting the third element of a list


Rest – extracts all the elements except the first.
First - extracts all the first elements.

HTML (Hypertext Markup Language)
 A seudolanguage
that includes marks that serve as
formatting hints and links to other files.
 An HTML file is made of text and tags.


An HTML file (page) is stored on the server and
can be download by a browser.
Browser –
removes the tags and interprets them as either
formatting hints or links to other files.
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>

Perl (Practical Extraction and Report Language)
a
programming language especially designed for
processing text.
 one of the most popular languages for writing CGI
scripts.
 CGI (Common Gateway Interface) programs are the
most common way for Web servers to interact
dynamically with users. Many HTML pages that
contain forms, for example, use a CGI program to
process the form's data once it's submitted.

SQL (Structured Query Language) –
a language used to answer queries about
database.
9.5
A PROCEDURAL
LANGUAGE:
C
Variables


Variables – names for memory locations.
Each memory location has an address.
 Used
by the computer internally
 Inconvenient for the programmer
Constants

constants – data values that cannot be changed
during the execution of a program.
constant – a = 2 * p * r ;
 Named constant – constant pi = 3.14;
 Symbolic constant - #define taxRate 0.0825
 Literal
Table 9.2 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 9.3 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 9.4 Logical operators
Operator
---------------!
&&
||
Definition
---------------NOT
AND
OR
Example
---------------------! ( Num1 < Num2 )
(Num1 < 5 ) && (Num2 > 10 )
(Num1 < 5 ) || (Num2 > 10 )
Table 9.5 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

Statement
 cause
an action to be performed
by the program.
 translates directly into one or
more executable instructions.
label:
goto label;

Statement
statement – a statement by placing a
semicolon(;) after it.
a++;
b = 4;
c = b + c * 4;
 Expression
statement – a unit of code consisting of
zero or more statements.
{
x = 1;
y = 20;
}
 Compound

Functions
 In
C, a subroutine is called a function.
 A C program is made of one or more functions,
one and only one of which must be called main.
 The
execution of the program always starts and ends
with main, but this function can call other functions.
 The function main is called by the operating system;
main in turn calls other functions.
When main is complete, control returns to the
operating system.

Side effect
Side effect of a function
 Is
an action that results in a change in the state of the
program.
 Occurs while the function is executing and before the
function returns.
 In
general,
the purpose of a function is
At the same time,
a function can have a side effect.
Function declaration

Parameter Passing

Pass by value
 Pass by reference
Actual parameters
Return type
Function header
Function body
Formal parameters

Parameter Passing
 Pass by value – a copy of data is created and
placed in a local variable in the called function.
by reference – sends the address of a
variable to the called function rather than
sending its value.
 Pass
Call by Value
main()
{
int a=1,b=2;
swap(a, b);
}
void swap(int x, int y)
{
int temp;
temp=x; x=y; y=temp;
}
a
b
1
2
1
2
y
x
temp
Call by Address (Reference)
main()
{
int a=1,b=2;
swap(&a, &b);
}
a
1000
b
2000
1
2
*y
*x
void swap(int *x, int *y) 1000
{
x
int temp;
temp=*x; *x=*y; *y=temp;
}
2000
y
temp
if-else statement
switch statement
while loop
for loop
False
do-while loop
Recursion



C language supports recursion.
A function in C can call itself.
int fac(int n)
{
if (n == 0)
return(1);
else
return( n * fact(n-1) );
}
Recursion



C language supports recursion.
A function in C can call itself.
int fac(int n)
{
if (n == 0)
return(1);
else
return( n * fac(n-1) );
}
The Towers of Hanoi


It is a puzzle about three poles and n disks of
increasing sizes. Initially, all the of the disks (all have
holes at their centers) are placed on the first pole. Our
goal is to transfer all the disks from the first pole to the
third. We can move only one disk at a time and it is
not allowed to place a larger disk on top of a smaller
one.
Let T(n) denote the number of moves.
Then T(n) = 2T(n-1) + 1. Finally we get T(n) = 2n - 1.
A
B
C
Recursive solution

Solve(n, A, B, C)
{
if (n == 1)
A→C
else
{
Solve(n-1, A, C, B)
Move from A → C
Solve(n-1, B, A, C)
}
}
n
A→C
B
n-1
A→B
C
A→C
n-1
B→C
A