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1 (variable) &( ) ( ) 0 9 A...Z a z under line( _ ) 1) (A...Z a z) 2) case sensitive 3) C/C++ (reserved word or key word) 1, 2,.., n char ch; int m; int n; int m, n; // float f = 10.0; // double d =f * 10.0; // float *ptr, a; // float *ptr; float a; byte sizeof sizeof // sizeof is a key word in C & C++ float f; sizeof(float) or sizeof(f) Pointer 1) 2) 3) pointer + k pointer k Pointer float a=1, b=2, c=3; float *fptr; fptr = &c; Show sizeof(char *)= sizeof(int *)= sizeof(double *)= C/C++ 程式設計 -1

2 * (array) ( constant pointer) [ ] Ex. float fa[2]; short int ia[4]; // sizeof(short int)=2 assumed &( ): 表示該 所在的位址 *( ): 存於此 的值或內容 fa[0] fa[1] ia[0] ia[1] ia[2] ia[3] * (index 0) (row major) int ia[4]={1,3,5; ia[0]=1; ia[1]=3, ia[2]=5, ia[3]=0 int m[2][3]={ 1, 2, 3, 4, 5, 6; int ma[2][3]={ 1, 2, 3, 4 ; int mb[2][3]={ { 1, 2, 3, { 4, 5, 6 ; int mc[2][3]= { { 1, 2, { 4 ; * compiler int ib[]={2,4,6,8; => int ib[4]={2,4,6,8; * ex. sizeof(ib)/sizeof(ib[0]); => As ib above, we get 4, the total elements of array ib; * (copy) ex. int iax[4]={5,4,3,8; int iay[4]; 1) iay=iax; // What's wrong? 2) for ( k=0; k<4; k++) iay[k]=iax[k]; // copy array elements one by one C/C++ 程式設計 -2

3 C++ operators are divided into 16 categories. The #1 category has the highest precedence; category #2 (Unary operators) takes second precedence, and so on to the Comma operator, which has lowest precedence. The operators within each category have equal precedence. The Unary (category #2), Conditional (category #14), and Assignment (category #15) operators associate right-to-left; all other operators associate left-to-right. Precedence of Operators Category Operator What it is (or does) 1. Highest () [] -> ::. 2. Unary! ~ & * sizeof new delete 3. Multiplicative * / % 4. Member access.* ->* 5. Additive Shift << >> 7. Relational < <= > >= 8. Equality == Function call Array subscript C++ indirect component selector C++ scope access/resolution C++ direct component selector Logical negation (NOT) Bitwise (1's) complement Unary plus Unary minus Preincrement or postincrement Predecrement or postdecrement Address Indirection (returns size of operand, in bytes) (dynamically allocates C++ storage) (dynamically deallocates C++ storage) Multiply Divide Remainder (modulus) C++ dereference C++ dereference Binary plus Binary minus Shift left Shift right Less than Less than or equal to Greater than Greater than or equal to Equal to Not equal to Association ( left-to-right ) right-to-left!= 9. & Bitwise AND 10. ^ Bitwise XOR 11. Bitwise OR 12. && Logical AND 13. Logical OR 14. Conditional?: (a? x : y means "if a then x, else y") right-to-left C/C++ 程式設計 -3

4 15. Assignment = *= /= %= += -= &= ^= = <<= >>= Simple assignment Assign product Assign quotient Assign remainder (modulus) Assign sum Assign difference Assign bitwise AND Assign bitwise XOR Assign bitwise OR Assign left shift Assign right shift 16. Comma, Evaluate All of the operators in this table can be overloaded except the following: right-to-left. C++ direct component selector.* C++ dereference :: C++ scope access/resolution?: Conditional (* Data copied from Turbo C++ 3.0, checks your compiler which you are using to make sure have same precedence as above showing. ) (* There are some compilers, one such as Java, the postincrement (++) and postdecrement (--) have higher precedence than equal sign, =, so the variables must be added 1 or subtracted 1 before assigning evaluated value to the variable at left of equal assign. ) * int *iptr; int a[5]; &a[2] => &(a[2]) // the address of element a[2] *iptr++ *=10; => *(iptr++) *=10; // *iptr = *iptr * 10; *iptr = *iptr *10 *stuptr.score[1] => *( (stuptr.score)[1] ) int *ary[10]; // ary, the array of int * with 10 elements int (*ary)[10]; // ary, a pointer points to int array with 10 elements float *pfun(); // pfun, a function returns float float (*pfun)(); // pfun, a pointer points to a function with float value return. C/C++ 程式設計 -4

5 int a[4]; a: 表示陣列開始的位址或更精確的說該陣列第㆒個元素所在的位址 &a: 陣列 a 的位址或陣列 a 從那㆒位址開始, 顯然 &a=a a[0]: 表示陣列第㆒個元素的內含值 以此例來說是㆒個整數 &a[0]: 表示陣列第㆒個元素所在的位址, 也就是說 : 陣列開頭的位址 於是有 : &a[0] = &a = a int a[10], float f[5]; int *iptr; float *fptr; iptr = a; fptr = f; // iptr,fptr 分別指向陣列 a, f * ( f + k ) = f [ k ] f fptr f+1 fptr+1 f+2 fptr+2 f+3 fptr+3 f+4 fptr+4 f[0]=*f f[1]=*(f+1) f[2]=*(f+2) f[3]=*(f+3) f[4]=*(f+4) a[0] a[1] a[2] a[3] a[4] a[5] a[6] a[7] a[8] a[9] iptr+0 iptr+1 iptr+2 iptr+3 iptr+4 iptr+5 iptr+6 iptr+7 iptr+8 iptr+9 ex. *(fptr) = *fptr => f[0]; *(fptr+3) => f[3]; *iptr+4 => (*iptr)+4 => a[0]+4 而不是 a[4] iptr + 1: 會指向 iptr 所指位址的 ㆒個整數的位址 fptr + 1: 會指向 fptr 所指位址的 ㆒個浮點數的位址 指標加 1: 表示指向 ㆒個元素, 至於元素的大小, 則依先前的宣告而定! 指標 (pointer): 與原先宣告的資料型態有很大的關係! C/C++ 程式設計 -5

6 * ( ) ex. string ( ) ex. a * 0 char [ ]; ex. char msg[10]= abc ; // ( 10-1 = 9) msg a b c \0 msg[5]= 6 ; msg= abc ; if msg[7]=0; then msg= a ; msg a \0 c \0 Ex. for (k=9; k>0; --k) { msg[k]=0; printf( %s\n, msg ); abc ab a C/C++ s1=s1+ test ; msg= testmsg ; msg * strlen(s) // strlwr(s) // strupr(s) // strcat(s1, s2) // s1 = s1+s2 s1 strcpy(s1, s2) // s1 = s2 s1 strcmp(s1, s2) int mystrlen(char *str) // less than s2, <0 { int len=0; // the same as s2, = 0 while (*str++) len++; // greater than s2, >0 return (len); C/C++ 程式設計 -6

7 float f; f 是 float *fptr; fptr 是個, 它可以存放 float 型態變數的位址 float **fpptr; fpptr 是個, 它可以存放 float 型態指標變數的位址 int a[6]; 位址 :a = &a[0], a + k = &a[0] + k ; 內容 :a[ k ]=*( a + k ) // Ex: a[3]=*(a+3); float af[3][4]; // row=3; column=4; 3 x 4 =12 int af 3 4 float *af = af[0] 4 float af *(af+0)+0 (*af)+1 (*af)+2 (*af)+3 af + 0 af[0][0] af[0][1] af[0][2] af[0][3] af + 1 af[1][0] af[1][1] af[1][2] af[1][3] af + 2 af[2][0] af[2][1] af[2][2] af[2][3] *(af+2)+0 *(af+2)+1 *(af+2)+2 *(af+2)+3 af : 表示陣列 af 的起始位址 = 第㆒列的起始位址 = af[0][0] 的位址 af+0: 是陣列 af 第 0 列的起始位址, 也就是 af[0][0] 的位址 = & af[0][0] af+k: 是陣列 af 第 k 列的起始位址, 也就是 af[k][0] 的位址 = & af[k][0] af[0][2] = *( *(af)+2 ) = *( *af+2 ) af[1][1] = *( *(af+1)+1 ) af[2][3] = *( *(af+2)+3 ) ( Recall:&( )= 該 的位址 ;*( )= 該 所存放的值或內容 ) 1) & af[1][1] 是否等於 *(af+1) + 1? 2) af[2] 等於 af+2 還是 *(af+2)? 3) 試著寫程式, 把各個元素的位址印出來, 以瞭解其排列與表示的方法 C/C++ 程式設計 -7

8 (structure) name Score1 Score2 John Melody Casey Vivian Mary array array array 當成結構 struct Student { char name[8]; int score1; int score2; ; // ; 莫忘 (structure) C/C++ struct struct structure_name { datatype data_member1; datatype data_member2;.. ; // ; 分號不可遺漏 ex. struct Birth { int year; unsigned char month; unsigned char day; ; // example for using structure // In C++, Birth mybirth;, works. struct Birth mybirth; mybirth.year=1999; mybirth.month=mybirth.month+1; scanf("%d", &mybirth.day); /* 結構的成員也可以是結構 */ struct Person { char name[8]; struct Birth birth; ; // example for using Person struct Person Me; Me.name="RichWang"; // error!! scanf("%s", Me.name); Me.brith.year=1963; Me.birth.month=10; scanf("%d", &Me.birth.day); Q: sizeof(birth)=? C/C++ 程式設計 -8

9 struct Student { struct Person person; float score[3]; ; struct Student struct Student stu; // stu 是結構變數,C++ 可省略 struct *stuptr; // stuptr 是存放某㆒ Student 結構位址的指標 stuptr=&stu; // stuptr 指向 stu 的位址或是說 stuptr 的值就是 stu 的位址 stu.score[0]=66; *stuptr.score[1]=70; // something wrong! 注意結合的優先順序! (*stuptr).score[1]=70; // O.K. 也可以寫成 stuptr->score[1] scanf("%f", &stu.score[2]); 參看 struct1.c, struct2.c, struct3.c, structdy.c Question : 1. char name[8]; char *name; 有何差異? 2. char name[10], *pname; a) scanf( %s, name); scanf( %s, pname); 何者合適? b) name= Kitty ; pname= Kitty, 何者正確? ( strcpy(mame, Kitty ) works.) enum 的使用 : enum: C/C++ enum 例如 : 水果 :orange banana apple watermelon 顏色 :Red Yellow Blue Brown Green 方向 :North East West South enum Fruit {orange, banana, apple, watermelon; // started from zero enum Direction {North=1, East, West, South; enum Color {Red, Green, Blue, Yellow=10, Brown; enum Boolean {false, true; 參看 enum.c C/C++ 程式設計 -9

10 1) auto (stack) ( ) 2) register auto 3) static ( ) 4) extern Link * (prototype) * * 1) 2) extern (global) 3) extern /* the program demos static variable */ #include "stdio.h" #include "conio.h" void CallStatic() { static int called=0; // look out "static" called++; printf("callstatic: I have been called %d times\n", called); void CallNormal() { int called=0; called++; printf("callnormal: I have been called %d times\n", called); void main() { int k; for (k=0; k<3; k++) CallStatic(); for (k=0; k<3; k++) CallNormal(); C/C++ 程式設計 -10

11 #define 的使用 : #define: 是種取代的作用 #define integer int // 自定資料型態 #define MAX 10 // 定義常數 #define Square(x) x*x // 定義函數 #define Square1(x) (x)*(x) // 注意與 Square 之差別 #define HighByte(x) ((x)>>8) & 0xFF #define Max(a,b) ((a)>(b))? (a) : (b) #define TurboC // 作為條件編譯時的識別字 // example for using #define : 1 #include "stdio.h" #include "conio.h" #define WORD unsigned int #define integer int // 自定資料型態 #define MAX 10 // 定義常數 #define Square(x) x*x // 定義函數 #define Square1(x) (x)*(x) // 注意與 Square 之差別 #define HighByte(x) ((x)>>8) & 0xFF #define Max(a,b) ((a)>(b))? (a) : (b) #define TurboC // 作為條件編譯時的識別字 void main() { unsigned int word=0x12ab; 條件編譯 #ifdef TurboC printf("sizeof(word)=%d\n", sizeof(word)); printf("sizeof(integer)=%d\n", sizeof(integer)); printf("max=%d\n", MAX); printf("square (1+2)=%d\n", Square (1+2)); printf("square1(1+2)=%d\n", Square1(1+2)); printf("high byte of %4x : %2x\n", word, HighByte(word)); printf("max(12, 33)=%d\n", Max(12, 33)); #endif C/C++ 程式設計 -11

12 union 的使用 : union: union union ThreeType { char ch; int i; float f; ; Q:sizeof(ThreeType)=? // example for using union : 1 #include "stdio.h" #include "conio.h" union TwoType { unsigned char ch; unsigned int i; ; TwoType twotype; twotype.i=0x1234; printf("twotype=%4x\n",twotype.i); twotype.ch=0xab; printf("twotype=%4x\n",twotype.i); Intel style : 資料儲存高高低低 union TwoType { unsigned char ch; unsigned int i; ; void main() { union TwoType twotype; // It s available in C++, TwoType twotype; printf("sizeof(twotype)=%d\n", sizeof(twotype)); twotype.i=0x1234; printf("twotype=%4x\n",twotype.i); twotype.ch=0xab; printf("twotype=%4x\n",twotype.i); twotype.i=0x4321; printf("twotype.ch=%4x\n", twotype.ch); C/C++ 程式設計 -12

13 typedef: 提供㆒種藉由類似變數宣告的方式, 來建立新的資料型態 ( 可以具有相當的複雜度 ) typedef: typedef float Vector[3]; // Vector: 表示具有㆔個 float 元素的㆒維陣列 float myvector[3]; Vector myvector; // 述兩種宣告, 具相同的效果 typedef int *IntPtr; IntPtr: 表示整數指標的資料型態 int *iptr; IntPtr iptr; // 述兩種宣告, 具相同的效果 typedef struct { char *name; int age; float weight; Person; Person: 表示包含 name,age,weight ㆔項資料成員的結構 讀取命令列的參數 : 若存在㆒可執行檔 :c:\result.exe, 可處理命令列的參數 C:\>Result argv[0] argv[1] argv[2] argv[3] 執行檔名稱 命令列參數 1 命令列參數 2 命令列參數 3 argc=4 * 程式可透過 列宣告, 來取得命令列參數 : void main(int argc, char **argv) #include "conio.h" #include "stdio.h" // >argmain xx yy // argc=3 // argv[0]="argmain", argv[1]="xx", argv[2]="yy" void main(int argc, char **argv) { printf("argc=%d\n", argc); C/C++ 程式設計 -13

14 宣告的方式 : void * malloc(size_t size); 1) size: 所需要的記憶體空間, 單位是 byte 2) 系統會在成功配置記憶體後, 傳回該記憶體區塊的起始位址 這時我們要 配合的做型態的轉換 (casting), 如此㆒來, 才可以透過指標的方式, 來對這 塊記憶體做存取 3) 當系統沒有足夠的記憶體空間時,malloc() 將傳回 NULL 於是我們可能就 需要結束程式, 並設法調整系統執行 的其他程式, 以便能空出足夠程式 執行的記憶體空間 4) 在動態記憶體配置的過程, 最好能在使用告㆒段落後, 便把該記憶體區 塊釋放,! 如果又需要配置計記憶體時, 再重新呼 叫 malloc() 即可 記憶體區塊釋放可用 free() Ex. int *iptr; // :iptr float *fptr; // :fptr iptr=(int *) malloc( 10*sizeof(int) ); // 要求配置儲存 10 個的 int 記憶體空間 fptr=(float *) malloc( 20 ); // do something here free(iptr); // 釋放配置的記憶體空間 free(fptr); // 釋放配置的記憶體空間 // C++ style iptr= new int [10]; fptr= new float [5]; // do something here delete [] iptr; delete [] fptr; // 要求配置儲存 5 (=20/4) 個的 float 記憶體空間 P.S.:(malloc() 與 free()); (new and delete)! C/C++ 程式設計 -14

15 #include "conio.h" #include "stdio.h" #include "stdlib.h" // for exit() // >result xx operator yy // argc=4 // argv[0]="...\result.exe", argv[1]="xx", argv[2]=operator, argv[3]="yy" // argv[0] : the executive program name include path void main(int argc, char **argv) { int k; char ch; float x, y, result; if ( argc!=4 ) { printf("\usage: result arg1 operator arg2\n"); printf("[ operator : +, -, *, / ]\n"); exit(0); // exit the program! ch=argv[2][0]; x=atof(argv[1]); y=atof(argv[3]); switch( ch ) { case '+' : result= x+y; break; case '-' : result= x-y; break; case '*' : result= x*y; break; case '/' : result= x/y; break; default : printf("this operator \"%s\" isn't available now!\n",argv[2]); exit(1); printf("result : %f\n", result); C/C++ 程式設計 -15

16 1) ASCII code 2) Scan code getch() ASCII code getch() getch() scan code #include "stdio.h" #include "conio.h" #define ESC 27 void main() { char ch; clrscr(); printf("===== Read pressing key program =====\n"); do { printf("press ESC to exit!\n"); ch=getch(); if ( ch==0 ) // special key pressed, ASCII value is 0 { ch=getch(); // get the scan code printf("00 %c \n",ch); else printf(" %c \n",ch); while( ch!=esc ); C/C++ 程式設計 -16