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C Program Design C Structures, Unions, Bit Manipulations and Enumerations

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  1. C Program DesignC Structures, Unions, Bit Manipulations and Enumerations 主講人:虞台文

  2. Content • Introduction • Structure Definitions • Initializing Structures • Accessing Members of Structures • Using Structures with Functions • typedef • Unions • Bitwise Operators • Bit Fields • Enumeration Constants

  3. C Program DesignC Structures, Unions, Bit Manipulations and Enumerations Introduction

  4. Main Topics • Structure • Collections of related variables (aggregates) under one name • Can contain variables of different data types • Commonly used to define records to be stored in files • Combined with pointers, can create linked lists, stacks, queues, and trees • Union • Allowed data type being overloaded • Bit fields • Enumeration

  5. C Program DesignC Structures, Unions, Bit Manipulations and Enumerations Structure Definitions

  6. Structure Definitions • A structure definition does not reserve space in memory. • Instead, creates a new data type used to define structure variables. struct PersonalData { char name[NAMESIZE]; char address[ADDRSIZE]; int YearOfBirth; int MonthOfBirth; int DayOfBirth; };

  7. Define Structure Variables (I) struct PersonalData { char name[NAMESIZE]; char address[ADDRSIZE]; int YearOfBirth; int MonthOfBirth; int DayOfBirth; }; struct PersonalData teacher, students[51], *p;

  8. Define Structure Variables (II) struct PersonalData { char name[NAMESIZE]; char address[ADDRSIZE]; int YearOfBirth; int MonthOfBirth; int DayOfBirth; }; struct PersonalData teacher, students[51], *p; struct PersonalData { char name[NAMESIZE]; char address[ADDRSIZE]; int YearOfBirth; int MonthOfBirth; int DayOfBirth; } teacher, students[51], *p; // variable identifier follows type

  9. Define Structure Variables (III) struct PersonalData { char name[NAMESIZE]; char address[ADDRSIZE]; int YearOfBirth; int MonthOfBirth; int DayOfBirth; }; struct PersonalData teacher, students[51], *p; struct PersonalData { char name[namesize]; char address[addresssize]; int YearOfBirth; int MonthOfBirth; int DayOfBirth; } teacher, students[51], *p; // variable identifier follows type typedef struct _tagPersonalData { char name[NAMESIZE]; char address[ADDRSIZE]; int YearOfBirth; int MonthOfBirth; int DayOfBirth; } PersonalData; PersonalData teacher, students[51], *p;

  10. struct PersonalData { char name[NAMESIZE]; char address[ADDRSIZE]; int YearOfBirth; int MonthOfBirth; int DayOfBirth; }; struct PersonalData x, teacher, students[51], *p; Valid Operations • Assigning a structure to a structure of the same type x = teacher; teacher = *p; students[i] = x; • Taking the address (&) of a structure p = &students[i]; • Accessing the members of a structure gets(students[0].name); p->YearOfBirth = 88; • Using the sizeof to determine the size of a structure size = sizeof(struct PersonalData); size = sizeof(x);

  11. #include <stdio.h> #define NAMESIZE 50 #define ADDRSIZE 80 struct PersonalData { char name[NAMESIZE]; char address[ADDRSIZE]; int YearOfBirth; int MonthOfBirth; int DayOfBirth; }; main() { struct PersonalData student; // Enter the student's record printf("Enter name of the student: "); gets(student.name); printf("Enter address: "); gets(student.address); printf("Enter birthday: yy/mm/dd: "); scanf("%2d/%2d/%2d", &student.YearOfBirth, &student.MonthOfBirth, &student.DayOfBirth); printf("\n\n"); // Print out the student record printf("Student name: %s\n", student.name); printf("Address: %s\n", student.address); printf("Bithday: %2d/%2d/%2d\n", student.YearOfBirth,student.MonthOfBirth, student.DayOfBirth); } Example

  12. #include <stdio.h> #define NAMESIZE 50 #define ADDRSIZE 80 struct PersonalData { char name[NAMESIZE]; char address[ADDRSIZE]; int YearOfBirth; int MonthOfBirth; int DayOfBirth; }; main() { struct PersonalData student; // Enter the student's record printf("Enter name of the student: "); gets(student.name); printf("Enter address: "); gets(student.address); printf("Enter birthday: yy/mm/dd: "); scanf("%2d/%2d/%2d", &student.YearOfBirth, &student.MonthOfBirth, &student.DayOfBirth); printf("\n\n"); // Print out the student record printf("Student name: %s\n", student.name); printf("Address: %s\n", student.address); printf("Bithday: %2d/%2d/%2d\n", student.YearOfBirth,student.MonthOfBirth, student.DayOfBirth); } Example

  13. #include <stdio.h> #define NAMESIZE 50 #define ADDRSIZE 80 struct PersonalData { char name[NAMESIZE]; char address[ADDRSIZE]; int YearOfBirth; int MonthOfBirth; int DayOfBirth; }; main() { struct PersonalData student; // Enter the student's record printf("Enter name of the student: "); gets(student.name); printf("Enter address: "); gets(student.address); printf("Enter birthday: yy/mm/dd: "); scanf("%2d/%2d/%2d", &student.YearOfBirth, &student.MonthOfBirth, &student.DayOfBirth); printf("\n\n"); // Print out the student record printf("Student name: %s\n", student.name); printf("Address: %s\n", student.address); printf("Bithday: %2d/%2d/%2d\n", student.YearOfBirth,student.MonthOfBirth, student.DayOfBirth); } Example getPersonInfo(&student); showPersonInfo(&student);

  14. // person.h #define NAMESIZE 50 #define ADDRSIZE 80 struct PersonalData { char name[NAMESIZE]; char address[ADDRSIZE]; int YearOfBirth; int MonthOfBirth; int DayOfBirth; }; void getPersonInfo(struct PersonalData *); void showPersonInfo(struct PersonalData *); Example // main.c #include <stdio.h> #include "person.h" main() { struct PersonalData student; // Enter the student's record getPersonInfo(&student); printf("\n\n"); // Print out the student record showPersonInfo(&student); }

  15. // person.h #define NAMESIZE 50 #define ADDRSIZE 80 struct PersonalData { char name[NAMESIZE]; char address[ADDRSIZE]; int YearOfBirth; int MonthOfBirth; int DayOfBirth; }; void getPersonInfo(struct PersonalData *); void showPersonInfo(struct PersonalData *); Example // person.c #include <stdio.h> #include "person.h" void getPersonInfo(struct PersonalData *p) { printf("Enter name: "); gets(p->name); printf("Enter address: "); gets(p->address); printf("Enter birthday: yy/mm/dd: "); scanf("%2d/%2d/%2d", &p->YearOfBirth, &p->MonthOfBirth, &p->DayOfBirth); } void showPersonInfo(struct PersonalData *p) { printf("Name: %s\n", p->name); printf("Address: %s\n", p->address); printf("Bithday: %2d/%2d/%2d\n", p->YearOfBirth, p->MonthOfBirth, p->DayOfBirth); } // main.c #include <stdio.h> #include "person.h" main() { struct PersonalData student; // Enter the student's record getPersonInfo(&student); printf("\n\n"); // Print out the student record showPersonInfo(&student); }

  16. // person.h #define NAMESIZE 50 #define ADDRSIZE 80 struct PersonalData { char name[NAMESIZE]; char address[ADDRSIZE]; int YearOfBirth; int MonthOfBirth; int DayOfBirth; }; void getPersonInfo(struct PersonalData *); void showPersonInfo(struct PersonalData *); Example // person.c #include <stdio.h> #include "person.h" void getPersonInfo(struct PersonalData *p) { printf("Enter name: "); gets(p->name); printf("Enter address: "); gets(p->address); printf("Enter birthday: yy/mm/dd: "); scanf("%2d/%2d/%2d", &p->YearOfBirth, &p->MonthOfBirth, &p->DayOfBirth); } void showPersonInfo(struct PersonalData *p) { printf("Name: %s\n", p->name); printf("Address: %s\n", p->address); printf("Bithday: %2d/%2d/%2d\n", p->YearOfBirth, p->MonthOfBirth, p->DayOfBirth); } // main.c #include <stdio.h> #include "person.h" main() { struct PersonalData student; // Enter the student's record getPersonInfo(&student); printf("\n\n"); // Print out the student record showPersonInfo(&student); }

  17. sizeof Operator structSomeData { charaChar; int anInt; floataFloat; double aDouble; }; sizeof(struct SomeData) = ?

  18. #include <stdio.h> #include <limits.h> #include <float.h> struct SomeData { char aChar; int anInt; float aFloat; double aDouble; }; main() { char mark[]={'M', 'A', 'R', 'K'}; struct SomeData x; printf("sizeof(struct SomeData) = %d\n\n", sizeof(struct SomeData)); x.aChar = 'A'; x.anInt = INT_MAX; x.aFloat = FLT_MAX; x.aDouble = DBL_MAX; printf("Address of x: %p\n", &x); printf("Address of x.aChar: %p\n", &x.aChar); printf("Address of x.anInt: %p\n", &x.anInt); printf("Address of x.aFloat: %p\n", &x.aFloat); printf("Address of x.aDouble: %p\n", &x.aDouble); } sizeof Operator

  19. #include <stdio.h> #include <limits.h> #include <float.h> struct SomeData { char aChar; int anInt; float aFloat; double aDouble; }; main() { char mark[]={'M', 'A', 'R', 'K'}; struct SomeData x; printf("sizeof(struct SomeData) = %d\n\n", sizeof(struct SomeData)); x.aChar = 'A'; x.anInt = INT_MAX; x.aFloat = FLT_MAX; x.aDouble = DBL_MAX; printf("Address of x: %p\n", &x); printf("Address of x.aChar: %p\n", &x.aChar); printf("Address of x.anInt: %p\n", &x.anInt); printf("Address of x.aFloat: %p\n", &x.aFloat); printf("Address of x.aDouble: %p\n", &x.aDouble); } sizeof Operator

  20. sizeof Operator • Because the size of data items of a particular type is machine dependent and because storage alignment considerations are machine dependent, so too is the representation of a structure. structSomeData { charaChar; int anInt; floataFloat; double aDouble; }; sizeof(struct SomeData) = ?

  21. C Program DesignC Structures, Unions, Bit Manipulations and Enumerations Initializing Structures

  22. Example // person.c #include <stdio.h> #include "person.h" void getPersonInfo(struct PersonalData *p) { printf("Enter name: "); gets(p->name); printf("Enter address: "); gets(p->address); printf("Enter birthday: yy/mm/dd: "); scanf("%2d/%2d/%2d", &p->YearOfBirth, &p->MonthOfBirth, &p->DayOfBirth); } void showPersonInfo(struct PersonalData *p) { printf("Name: %s\n", p->name); printf("Address: %s\n", p->address); printf("Bithday: %2d/%2d/%2d\n", p->YearOfBirth, p->MonthOfBirth, p->DayOfBirth); } // person.h #define NAMESIZE 50 #define ADDRSIZE 80 struct PersonalData { char name[NAMESIZE]; char address[ADDRSIZE]; int YearOfBirth; int MonthOfBirth; int DayOfBirth; }; void getPersonInfo(struct PersonalData *); void showPersonInfo(struct PersonalData *);

  23. Example // person.c #include <stdio.h> #include "person.h" void getPersonInfo(struct PersonalData *p) { printf("Enter name: "); gets(p->name); printf("Enter address: "); gets(p->address); printf("Enter birthday: yy/mm/dd: "); scanf("%2d/%2d/%2d", &p->YearOfBirth, &p->MonthOfBirth, &p->DayOfBirth); } void showPersonInfo(struct PersonalData *p) { printf("Name: %s\n", p->name); printf("Address: %s\n", p->address); printf("Bithday: %2d/%2d/%2d\n", p->YearOfBirth, p->MonthOfBirth, p->DayOfBirth); } • // main.c • #include <stdio.h> • #include "person.h" • main() • { • struct PersonalData student = { • "Hale-Evans, Ron", • "Seattle, Washington", • 1965, • 6, • 27 • }; • // Print out the student record • showPersonInfo(&student); • } // person.h #define NAMESIZE 50 #define ADDRSIZE 80 struct PersonalData { char name[NAMESIZE]; char address[ADDRSIZE]; int YearOfBirth; int MonthOfBirth; int DayOfBirth; }; void getPersonInfo(struct PersonalData *); void showPersonInfo(struct PersonalData *);

  24. Example // person.c #include <stdio.h> #include "person.h" void getPersonInfo(struct PersonalData *p) { printf("Enter name: "); gets(p->name); printf("Enter address: "); gets(p->address); printf("Enter birthday: yy/mm/dd: "); scanf("%2d/%2d/%2d", &p->YearOfBirth, &p->MonthOfBirth, &p->DayOfBirth); } void showPersonInfo(struct PersonalData *p) { printf("Name: %s\n", p->name); printf("Address: %s\n", p->address); printf("Bithday: %2d/%2d/%2d\n", p->YearOfBirth, p->MonthOfBirth, p->DayOfBirth); } • // main.c • #include <stdio.h> • #include "person.h" • main() • { • struct PersonalData persons[] = { • {"Hale-Evans, Ron", "Seattle, Washington", 1965, 6, 27}, • {"Liddell, Alice", "Wonderland", 1852, 5, 4}, • {"Adams, Douglas", "The Galaxy", 1961, 11, 15} • }; • struct PersonalData *p; • int i; • // Print out the records • for(i = 0, p = persons; i < sizeof(persons)/sizeof(struct PersonalData); i++){ • ShowPersonInfo(p++); • printf("\n"); • } • } // person.h #define NAMESIZE 50 #define ADDRSIZE 80 struct PersonalData { char name[NAMESIZE]; char address[ADDRSIZE]; int YearOfBirth; int MonthOfBirth; int DayOfBirth; }; void getPersonInfo(struct PersonalData *); void showPersonInfo(struct PersonalData *);

  25. Example // person.c #include <stdio.h> #include "person.h" void getPersonInfo(struct PersonalData *p) { printf("Enter name: "); gets(p->name); printf("Enter address: "); gets(p->address); printf("Enter birthday: yy/mm/dd: "); scanf("%2d/%2d/%2d", &p->YearOfBirth, &p->MonthOfBirth, &p->DayOfBirth); } void showPersonInfo(struct PersonalData *p) { printf("Name: %s\n", p->name); printf("Address: %s\n", p->address); printf("Bithday: %2d/%2d/%2d\n", p->YearOfBirth, p->MonthOfBirth, p->DayOfBirth); } • // main.c • #include <stdio.h> • #include "person.h" • main() • { • struct PersonalData persons[] = { • {"Hale-Evans, Ron", "Seattle, Washington", 1965, 6, 27}, • {"Liddell, Alice", "Wonderland", 1852, 5, 4}, • {"Adams, Douglas", "The Galaxy", 1961, 11, 15} • }; • struct PersonalData *p; • int i; • // Print out the records • for(i = 0, p = persons; i < sizeof(persons)/sizeof(struct PersonalData); i++){ • ShowPersonInfo(p++); • printf("\n"); • } • } // person.h #define NAMESIZE 50 #define ADDRSIZE 80 struct PersonalData { char name[NAMESIZE]; char address[ADDRSIZE]; int YearOfBirth; int MonthOfBirth; int DayOfBirth; }; void getPersonInfo(struct PersonalData *); void showPersonInfo(struct PersonalData *);

  26. Example // person.c #include <stdio.h> #include "person.h" void getPersonInfo(struct PersonalData *p) { printf("Enter name: "); gets(p->name); printf("Enter address: "); gets(p->address); printf("Enter birthday: yy/mm/dd: "); scanf("%2d/%2d/%2d", &p->YearOfBirth, &p->MonthOfBirth, &p->DayOfBirth); } void showPersonInfo(struct PersonalData *p) { printf("Name: %s\n", p->name); printf("Address: %s\n", p->address); printf("Bithday: %2d/%2d/%2d\n", p->YearOfBirth, p->MonthOfBirth, p->DayOfBirth); } • // main.c • #include <stdio.h> • #include "person.h" • main() • { • struct PersonalData persons[] = { • {"Hale-Evans, Ron", "Seattle, Washington", 1965, 6, 27}, • {"Liddell, Alice", "Wonderland", 1852, 5, 4}, • {"Adams, Douglas", "The Galaxy", 1961, 11, 15} • }; • struct PersonalData *p; • int i; • // Print out the records • for(i = 0, p = persons; i < sizeof(persons)/sizeof(struct PersonalData); i++){ • ShowPersonInfo(p++); • printf("\n"); • } • } // person.h #define NAMESIZE 50 #define ADDRSIZE 80 struct PersonalData { char name[NAMESIZE]; char address[ADDRSIZE]; int YearOfBirth; int MonthOfBirth; int DayOfBirth; }; void getPersonInfo(struct PersonalData *); void showPersonInfo(struct PersonalData *);

  27. Initializing Structures • // initialized when defined • struct PersonalData persons[] = { • {"Hale-Evans, Ron", "Seattle, Washington", 1965, 6, 27}, • {"Liddell, Alice", "Wonderland", 1852, 5, 4}, • {"Adams, Douglas", "The Galaxy", 1961, 11, 15} • }; • struct PersonalData classLeader, friend; • // initialized using assignment operator • classLeader = persons[1]; • // Initialized field by field • strcpy(friend.name, "George Lin"); • strcpy(friend.address, "Taipei Taiwan"); • friend.YearOfBirth = 1978; • friend.MonthOfBirth = 12; • friend.DayOfBirth = 24;

  28. Initializing Structures • // initialized when defined • struct PersonalData persons[] = { • {"Hale-Evans, Ron", "Seattle, Washington", 1965, 6, 27}, • {"Liddell, Alice", "Wonderland", 1852, 5, 4}, • {"Adams, Douglas", "The Galaxy", 1961, 11, 15} • }; • struct PersonalData classLeader, friend, *p; • // initialized using assignment operator • classLeader = persons[1]; • // Initialized field by field using a pointer • p = &friend; • strcpy(p->name, "George Lin"); • strcpy(p->address, "Taipei Taiwan"); • p->YearOfBirth = 1978; • p->MonthOfBirth = 12; • p->DayOfBirth = 24;

  29. C Program DesignC Structures, Unions, Bit Manipulations and Enumerations Accessing Members of Structures

  30. Accessing structure members • Dot operator (.) for structure variables struct PersonalData friend; strcpy(friend.name, "George Lin"); strcpy(friend.address, "Taipei Taiwan"); friend.YearOfBirth = 1978; friend.MonthOfBirth = 12; friend.DayOfBirth = 24; • Arrow operator (->) for pointers struct PersonalData friend, *p; p = &friend; strcpy(p->name, "George Lin"); strcpy(p->address, "Taipei Taiwan"); p->YearOfBirth = 1978; p->MonthOfBirth = 12; p->DayOfBirth = 24;

  31. equivalent More on Arrow Operator • Dot operator (.) for structure variables struct PersonalData friend; strcpy(friend.name, "George Lin"); strcpy(friend.address, "Taipei Taiwan"); friend.YearOfBirth = 1978; friend.MonthOfBirth = 12; friend.DayOfBirth = 24; • Arrow operator (->) for pointers struct PersonalData friend, *p; p = &friend; strcpy(p->name, "George Lin"); strcpy(p->address, "Taipei Taiwan"); p->YearOfBirth = 1978; p->friend.MonthOfBirth = 12; p->DayOfBirth = 24; struct PersonalData friend, *p; p = &friend; strcpy((*p).name, "George Lin"); strcpy((*p).address, "Taipei Taiwan"); (*p).YearOfBirth = 1978; (*p).friend.MonthOfBirth = 12; (*p).DayOfBirth = 24;

  32. C Program DesignC Structures, Unions, Bit Manipulations and Enumerations Using Structures with Functions

  33. typedef struct_tagComplex { doublereal; doubleimag; } Complex; ParameterPassings • Passing Value Complex AddByVal(Complex a, Complex b); • Passing Reference void AddByRef(const Complex *a, const Complex *b, Complex *c);

  34. // complex.h typedefstruct _tagComplex { double real; double imag; } Complex; Complex AddByVal(Complex, Complex); void AddByRef(Complex*, Complex*, Complex*); Example // complex.c #include "complex.h" Complex AddByVal(Complex a, Complex b) { Complex c; c.real = a.real + b.real; c.imag = a.imag + b.imag; return c; } void AddByRef(Complex* a, Complex* b, Complex* c) { c->real = a->real + b->real; c->imag = a->imag + b->imag; }

  35. // complex.h typedefstruct _tagComplex { double real; double imag; } Complex; Complex AddByVal(Complex, Complex); void AddByRef(Complex*, Complex*, Complex*); Example // main.c #include <stdio.h> #include "complex.h" main() { Complex x = {12.0, 5}; Complex y = {4.0, 8.0}; Complex z, w; // Call by value z = AddByVal(x, y); printf("(%.1f + i%.1f) + (%.1f + i%.1f) = (%.1f + i%.1f)\n", x.real, x.imag, y.real, y.imag, z.real, z.imag); // Call by reference AddByRef(&x, &y , &w); printf("(%.1f + i%.1f) + (%.1f + i%.1f) = (%.1f + i%.1f)\n", x.real, x.imag, y.real, y.imag, w.real, w.imag); } // complex.c #include "complex.h" Complex AddByVal(Complex a, Complex b) { Complex c; c.real = a.real + b.real; c.imag = a.imag + b.imag; return c; } void AddByRef(Complex* a, Complex* b, Complex* c) { c->real = a->real + b->real; c->imag = a->imag + b->imag; }

  36. Passing arrays by value • Create a structure with the array as a member • Pass the structure

  37. C Program DesignC Structures, Unions, Bit Manipulations and Enumerations typedef

  38. typedef • Creates synonyms for previously defined data types • typedef does not create a new data type • Only creates an alias • Create shorter type names • Make a program more portable. typedeftype-declaration synonym;

  39. Example // complex.h struct _tagComplex { double real; double imag; }; typedef struct _tagComplex Complex; typedef struct _tagComplex *ptrComplex; Complex AddByVal(Complex, Complex); void AddByRef(ptrComplex, ptrComplex, ptrComplex);

  40. Some More Examples // complex.h struct _tagComplex { double real; double imag; }; typedef struct _tagComplex Complex; typedef struct _tagComplex *ptrComplex; Complex AddByVal(Complex, Complex); void AddByRef(ptrComplex, ptrComplex, ptrComplex); // SomeTypeDef.h #include "complex.h" typedefchar CHAR; typedef CHAR* PSTR; typedefunsigned char BYTE; typedefint INT; typedefunsigned UINT; typedef UINT DWORD; typedef Complex (*COMPLEXOP)(Complex, Complex); typedef INT (*ARITHOP)(INT, INT); INT sum(INT a, INT b); INT substract(INT a, INT b); INT mul(INT a, INT b); INT div(INT a, INT b);

  41. Some More Examples /* arith.c */ #include <SomeTypedef.h> INT sum(INT a, INT b) { return a + b; } INT substract(INT a, INT b) { return a - b; } INT mul(INT a, INT b) { return a * b; } INT div(INT a, INT b) { if(b) return a / b; else return 0; } // complex.h struct _tagComplex { double real; double imag; }; typedef struct _tagComplex Complex; typedef struct _tagComplex *ptrComplex; Complex AddByVal(Complex, Complex); void AddByRef(ptrComplex, ptrComplex, ptrComplex); // SomeTypeDef.h #include "complex.h" typedefchar CHAR; typedef CHAR* PSTR; typedefunsigned char BYTE; typedefint INT; typedefunsigned UINT; typedef UINT DWORD; typedef Complex (*COMPLEXOP)(Complex, Complex); typedef INT (*ARITHOP)(INT, INT); INT sum(INT a, INT b); INT substract(INT a, INT b); INT mul(INT a, INT b); INT div(INT a, INT b);

  42. Some More Examples #include <stdio.h> #include "SomeTypedef.h" ARITHOP arith[4]={sum, substract, mul, div}; main() { INT val1, val2, op; printf("Enter two numbers: "); scanf("%d %d", &val1, &val2); printf("0: Add, 1: Sub, 2: Mul, 3: Div\n"); do { printf("Enter number of operation: "); scanf("%d", &op); } while(op<0 || op>3); printf("%d", (*arith[op])(val1, val2)); } // complex.h struct _tagComplex { double real; double imag; }; typedef struct _tagComplex Complex; typedef struct _tagComplex *ptrComplex; Complex AddByVal(Complex, Complex); void AddByRef(ptrComplex, ptrComplex, ptrComplex); // SomeTypeDef.h #include "complex.h" typedefchar CHAR; typedef CHAR* PSTR; typedefunsigned char BYTE; typedefint INT; typedefunsigned UINT; typedef UINT DWORD; typedef Complex (*COMPLEXOP)(Complex, Complex); typedef INT (*ARITHOP)(INT, INT); INT sum(INT a, INT b); INT substract(INT a, INT b); INT mul(INT a, INT b); INT div(INT a, INT b);

  43. Some More Examples #include <stdio.h> #include "SomeTypedef.h" ARITHOP arith[4]={sum, substract, mul, div}; main() { INT val1, val2, op; printf("Enter two numbers: "); scanf("%d %d", &val1, &val2); printf("0: Add, 1: Sub, 2: Mul, 3: Div\n"); do { printf("Enter number of operation: "); scanf("%d", &op); } while(op<0 || op>3); printf("%d", (*arith[op])(val1, val2)); } // complex.h struct _tagComplex { double real; double imag; }; typedef struct _tagComplex Complex; typedef struct _tagComplex *ptrComplex; Complex AddByVal(Complex, Complex); void AddByRef(ptrComplex, ptrComplex, ptrComplex); // SomeTypeDef.h #include "complex.h" typedefchar CHAR; typedef CHAR* PSTR; typedefunsigned char BYTE; typedefint INT; typedefunsigned UINT; typedef UINT DWORD; typedef Complex (*COMPLEXOP)(Complex, Complex); typedef INT (*ARITHOP)(INT, INT); INT sum(INT a, INT b); INT substract(INT a, INT b); INT mul(INT a, INT b); INT div(INT a, INT b);

  44. Exercise • Implement a program similar to the above example but for complex numbers.

  45. C Program DesignC Structures, Unions, Bit Manipulations and Enumerations Unions

  46. union • It is sometimes desirable to define a variable which can be of two or more different types according to different circumstances (overloading). • The distinction between a union and a structure: • The members of a structure define different variables • The members of a union define different manifestations of the same variable. • The space need only be allocated to accommodate the largest type specified in a union.

  47. union Definition typedef union _tagRemark { int age; double tall; char month[4]; } REMARK; REMARK rem; union Remark { int age; double tall; char month[4]; } rem; union Remark { int age; double tall; char month[4]; }; union Remark rem; sizeof(union Remark)=? sizeof(REMARK)=?

  48. Valid union Operations • Assignment to union of same type: = x = y; y = *p; • Taking address: & p = &x; • Accessing union members: . int n = x.age; printf("%s\n", y.month); • Accessing members using pointers: -> int m = p->age; printf("%s\n", p->month); union Remark { int age; double tall; char month[4]; } x, y, *p;

  49. Example // main.c #include <stdio.h> #include <string.h> #include "remark.h" void ShowData(VarRemark data) { switch(data.typeRemark){ case 0: printf("Age = %d\n", data.rem.age); break; case 1: printf("Tall = %f\n", data.rem.tall); break; case 2: printf("Month = %s\n", data.rem.month); break; } } main() { VarRemark datas[3]={{0, 35}, {1}, {2}}; int i; datas[1].rem.tall = 174.5; strcpy(datas[2].rem.month, "Jul"); for(i=0; i< sizeof(datas) / sizeof(VarRemark); i++) ShowData(datas[i]); } // remark.h typedefunion _tagRemark { int age; double tall; char month[4]; } REMARK; typedefstruct _tagVarRemark { int typeRemark;// 0: age // 1: tall // 2: month REMARK rem; } VarRemark; A union may only be initialized with a value of the type of its first member.

  50. Example // main.c #include <stdio.h> #include <string.h> #include "remark.h" void ShowData(VarRemark data) { switch(data.typeRemark){ case 0: printf("Age = %d\n", data.rem.age); break; case 1: printf("Tall = %f\n", data.rem.tall); break; case 2: printf("Month = %s\n", data.rem.month); break; } } main() { VarRemark datas[3]={{0, 35}, {1}, {2}}; int i; datas[1].rem.tall = 174.5; strcpy(datas[2].rem.month, "Jul"); for(i=0; i< sizeof(datas) / sizeof(VarRemark); i++) ShowData(datas[i]); } // remark.h typedefunion _tagRemark { int age; double tall; char month[4]; } REMARK; typedefstruct _tagVarRemark { int typeRemark;// 0: age // 1: tall // 2: month REMARK rem; } VarRemark;