1

First Step to

C Language

2

Online

• Programming Language

• Introduction of C Language

• Simple Example

3

Programming Language

High-LevelLanguages

Assembly Languageor Low-levelLanguage

Machine Language

Machine

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Program Execution

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

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.

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

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

VB 程式Sum = Val(Text1.Text) + Val(Text2.Text)

+ Val(Text3.Text)

Ave = Sum /3

Print " 平均分數 = "; Ave

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.