1 First Step to C Language 2 Online Programming Language Introduction of C Language Simple Example.
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Transcript of 1 First Step to C Language 2 Online Programming Language Introduction of C Language Simple Example.
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1
First Step to
C Language
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Online
• Programming Language
• Introduction of C Language
• Simple Example
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Programming Language
High-LevelLanguages
Assembly Languageor Low-levelLanguage
Machine Language
Machine
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Program Execution
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程式語言( Programming language )
• 我們可以定義一種比較類似人類說話的語言( Language ),用來撰寫程式,取代機器語言。
• 機器語言: 0 , 1 所組成的表示法– Example : 20A3 ( R0A3 )
• 低階語言:與處理器( Processor )相關– Example : Assembly , load R0,#A3H
• 高階語言:更接進人類語言或視覺傳達 – Example : C 、 VB , a=163
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轉譯程式( Translator )• 轉譯程式( Translator ):一種系統軟體, 將輸入的原始程式轉換成另一種相對應的程式語言。– 原始程式( Source program )– 目的程式( Object program )
原始程式(Source Program)
Text file
轉譯程式
Translator
目的程式(Object Program)
Text file orExecution file
ex:20A3 ex: a=163
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Low Level Language
• Every CPU has its machine language.
• CPU only understand its machine language.
• Usually, the CPU manufactory creates an assembly language for it.– Example: 8051, 8088 assembly language
• Of course, we need a translator -- assembler -- to translate the program written by the assembly language to the machine code.
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High Level Language
• Algo (1960)
• FORTRAN (1957)
• C (1970)
• Pascal (1971)
• Basic 、 VB 、 VC........
• The translator for high level language is called compiler or interpreter.
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Compiler (編譯程式)• 將高階語言所寫的程式 (included a file) 翻譯成為機器語言程式 (another execution file)
• Example : C 、 C++ 、 Fortran 、 Pascal
高階語言程式sample1.c(a text file)
編譯程式Compiler
g++
目的程式h1*
(an executable file)
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Building a Program in C
檔案為sample1.c
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Interpreter (直譯程式)• 將程式一行一行讀入,每讀入一行便將其翻譯成為機器碼並執行之。執行完畢再進行下一行的解譯。
• Example : BASIC 、 Shell 、 VB
高階語言程式project.vbp
直譯程式Interpreter
VB
執行結果
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VB 程式Sum = Val(Text1.Text) + Val(Text2.Text)
+ Val(Text3.Text)
Ave = Sum /3
Print " 平均分數 = "; Ave
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Preprocessor (前置處理程式)• 將某一種高階語言所寫的程式翻譯成為另一種高階程式語言程式
高階語言程式Fortran 77
前置處理程式
Preprocessor
目的程式Fortran IV
目的程式Object Code
目的程式Fortran IV
Fortran IV 編譯程式
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Introduction of C
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History of C Language (1/2)• In 1960 , Algo 60 ( International Committee )
• In 1963 ,劍橋大學和倫敦大學以 ALGOL 60 為基礎,共同推出了 CPL (Combined Programming Language) 語言。
• In 1966 ,劍橋大學的 Martin Richards 對 CPL 語言做了簡化,推出了 BCPL (Basic Combined Programming Language) 語言。
• In 1970 , AT&T 的 Ken Thompson 以 BCPL 語言為基礎簡化了 BCPL 語言,設計出 B 語言,並利用 B 語言寫出早期的 UNIX 作業系統。
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History of C Language (2/2)• In 1972, AT&T. 的 Dennis Ritchie 以 B 語言為基礎,設計出 C 語言 ( 取 BCPL 的第二個字母 ) 。之後 Ken Thompson 和 Dennis Ritchie 兩人又合力利用 C 語言寫出了新版的 UNIX 作業系統。
• In 1983 , AT&T. 的 Bjarne Sroustrup 於 C 語言中加入 class ( 類別 ) 的概念,以及物件導向的概念,產生出 C++ 語言。
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C & C++
• C++ is an extension of C language.– C++ has object-oriented concept– 在 C 中使用 class 的語法表示 object.– C++ is called as “C with a class”
• No object: 即使是針對同件事物 , 每一個參數各自獨立運作 .
• Object-oriented: 針對同件事物 , 把所有的參數 , 與其上的操作包裹起來 .
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Rectangle (1)
width
height
• Attribute: – Width=2– Height=1– You can’t access them directly.
• Function:
– area()=width * height– perimeter()=2(width+height)
width=2,height=1
area(),perimeter()
如此就可以避免粗心大意的程式設計師改掉 attribute 中的資料 !
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Rectangle (2)
width
height
• Attribute: – width– height– You can’t access them directly.
• Function: – Set width– Set height– area()=width * height– perimeter()=2(width+height)
width,height
area(),perimeter()
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Object
• An object = the data + member functions– Data owns the value or attributes.– Only member function can access the data.
• In C, we use “class” to define the data structure of your object.
• A class can create a copy of object.
Data: x
member functions: add x : x=x+1 sub x : x=x-1
an Object
or a member of a class
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Class and Subclass• 長方形
– 正方形長方形 is a class
正方形是長方形的subclass
• 動物– 昆蟲
• 蝴蝶• 蟬
– 鳥– 爬蟲類
• 交通工具– 汽車
• 轎車• 跑車
– 火車交通工具 is a class
汽車是交通工具的 subclass
汽車 is a class
轎車是汽車的 subclass
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Class – Car Example
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Inheritance
• Classes has inheritance.
• Base class Derived class– Derived class has all attributes of base class and
itself attributes.
traffic tools
car
train
如此程式碼就可以reuse!
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Square
width
height
• Square is a rectangle
• Attribute: – width– height=width– You can’t access them directly.
• Function: – Set width– area()=width * height– perimeter()=2(width+height)
width,height
area(),perimeter()
width
width
area()perimeter()
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Overload
• “+” is the add operation for integers.– “a++” means “a=a+1”.
• However, these operations is not defined for other classes.– You can define the functions for these symbols.– Example: a object “WaitTime”, define that
“WaitTime++” means a random number between 0 and 30. 所有的運算 (*,+,...) 本
來就“有”明確定義出其的使用的資料範圍 !
內訂運作於 integer!
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Overload Square
• A is a square.
• Function: – area(A)=width * height– A**=area(A)– perimeter(A)=2(width+height)– A++ = perimeter(A)
width
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sample1.c
#include < cstdio> /* or #include <stdio.h> */
main( )
{ int i=0 ; /* variable declaration */
i=i+1; /* variable operation */ printf("i=%d\n",i) ; /* output to screen */}
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Notes
1. { 與 } 符號表示程式或敘述的開始與結 束 .
2. ; 符號表示變數宣告或指令敘述的段落 .
3. /* 與 */ 符號表示程式內註解 .
4. 主程式為 C 程式執行之進入點 .
5. 上述所提到之副程式不一定存在於整個程式中 , 但是主程式必需存在 .
6. C compiler 不管空格 , 但請保持良好的寫作格式 .
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C Compiler
C program C Compiler Executable Output File
sampe1.c h1g++
pure text file
an execution file for translation
execution file
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Compile Your Program 1
>g++ -o h1 sample1.c
C complier output file Your C program
> h1 Begin to execute
i=1
>
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sample2.c#include <iostream>
using namespace std;
main()
{
int num = 2;
char sym_1 = 'c';
cout << "Give me "<< num << " scoops of \n";
cout << " " << sym_1 << "ho" << sym_1 << "olate, ";
cout << " " << sym_1 << "ho" << sym_1 << "olate, \n";
cout << "Please!\n";
}
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Compile Your Program 2
>g++ -o h2 sample2.c
> h2
Give me 2 scoops of
chocolate, chocolate,
Please!
>
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Header Files
#include <iostream>
using namespace std;– This command tells C compiler to include the file
“iostream.h” before compiling.– The files included are called as header files.
#include "event.h" – If you use “...” rather than <...>, then C compiler
will find this included file “event.h” from the directory of the main program.
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C Preprocessor
• The C preprocessor and compiler combine together.
• C preprocessor parses the C program first. It translates some commands and still gives another C programs as output.
• For example: #include < stdio.h > or
#include <cstdio>– C preprocessor will find the file stdio.h and include it
to your C program.
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Output in C++
#include <iostream>
using namespace std;
cout << “C out” ;– cout is an object.– cout reads data put after << commands.– << is an insert operator of cout.– Data is sent to the standard output.– Usually, your monitor is the standard output.
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Errsample1.c
#include < cstdio> main( ) { int i=0 ;
i=i+1 /* ; is lost */ printf("i=%d\n",i) ; }
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Syntax Error Occurs
>g++ -o h3 Errsample1.c
Errsample1.c: In function `int main()':
Errsample1.c:7: parse error before `( '
>
All of the errors list
and no output file h3 exists
• Syntax :語法 ==> 程式的寫法
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Errsample2.c
#include < cstdio > main( ) { int i=0 ;
i=i+1; /* variable operation */ printf("i=%d\n", &i) ; /* output error */}
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Semantic Error Occurs
>g++ -o a.out Errsample2.c
>a.out
i = -1073743372
>
output file a.out exists
but output i’s address -> Error!
• Semantic :語意 ==> 程式的意義• Semantic error! Run time error!
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Set Path
• If you can’t use g++?
• copy .cshrc to your home directory– We use tcsh shell.
• Set path – set path = (/bin /usr/bin /usr/ucb
/usr/local/bin /usr/etc /etc .)
• You can find the directory of g++ by “whereis g++”.
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C Instructions
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Variable
• Variables are temporary memory to save some important values.
• Each variable needs a name as well as its data type.– Ex: i is an integer.
name data type
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Variable Name
• C allows a variable-length name. However, only the first 32 characters is useful.
• You can use alphabet, number, underline for your name.
• First character must be an alphabet. – Example: var1, a, string_name, StringName
• Capital and small alphabet is different in C.– Example: “Var” and “var” are different.
• Keyword can’t be variable name.
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Data type
• A data type is an abstract representation of stored data.
• Every data type has it scope. – int: -32768 32767 (16 bits)– long: -2147483648 2147483647 (32 bits)– unsigned int: 0 65535 (16 bits)– unsigned long: 0 4294967295 (32 bits)– float: (+-)10^-38 10^38 (32 bits)– double: (+-) 10^-308 10^308 (64 bits)– char: 0 255 (8 bits ASCII)
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Declaration
int i; /* i is an integer */
double abc; /* abc is a floating point. */
char A1; /* A1 is a character */– We need to declare the variable before it is
used.– That is , bind its name and its data type.– We can change the values of variables by
assignment.
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Assignment
i=20; /* i has a new value 20 */
abc=3.14; /* abc has value 3.14 */
A1=‘a’; /*A1 has value 61h */
B1=‘\a’; /* B1 has value 07h */– Assign the value to a variable that has been
declared.
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Constant
#define PI 3.141592
#define FileName “sample1.c”– We can’t change the value of constant if it has
been defined.
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Escape Sequence
• Some characters used to represent special functions are called as escape sequence.\a beep \\ backslash \
\b backspace \’ single quote ’
\f form feed \’’ double quote ’’
\r carriage return \xhh hexadecimal
\t tab \n new line (endl)– Ex: cout << “Hi! \n” ;
cout << “\‘‘ Hi!\’’ she said” << endl;
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Output in C
#include <cstdio>
int i =1;
printf ("Hi");
printf(“i=%d" , i); – printf send the string to the standard output.– If you want to send the value of variable to
screen, you need to use the string format to denote the variable.
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String Format
%c char
%s char [n]
%d int
%i int
st=‘A’;
printf(“The character is %c \n”, st);
printf(“PI is %f, i is %d. \n”, PI, i);
%f float
%ld long
%lf double
%Lf long double
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Format Modify
printf("a=%.2f\n",a) ;
printf("a=%10.2f\n",a);
printf("i=%4d\n",i);
printf("i=%04d\n",i);
a=12.35
a= 12.35
i= 12
i=0012
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Output Format
• Operator “setw” can set the format of output string.
#include <iomanip>
cout << setw(8) << "LOC:" << setw(10) << "Taiwan" << setw(3) << i << endl;
Loc: Taiwan 1
8 chars 10 chars 3 chars
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Input in C++
#include <iostream>
using namespace std;
double abc;
cin >> abc ; /* read and save abc */– cin is an object:– cin get data value from the standard input.– Usually, your keyboard is the standard input.
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Input in C
#include <cstdio>
printf("Please input an integer :") ;
scanf("%d", &i);
printf("Please input a floating point number:") ;
scanf("%f", &a);– & is called as “address-of operator”.– &a means the address of a.
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Arithmetic Operators
• a=7+1; /* a=8 */
• b=5-3; /* b=2 */
• c=a*b; /* c=16 */
• d=a/b; /* d=4 */
• e=a%b; /* e=0 */
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Homework• 尋找 C 語言的由來與其演進• Please write a program to read two floating
point numbers, add them and show the result on screen.
• Please write a program to read the temperature in Fahrenheit and show it in Celsius degree.– You must have commands and beautiful format.– Print your program and results.