Basic Data types in C Τι πρέπει να ξέρετε ήδη

και αν όχι, χρειάζεται να το μάθετε

• int

• char

• float

• double

Variable declaration in C:

int x, y, z; Example:

Variable assignment:

x = 35; Example:

type variables / instances

value

Boolean

•Has two values, true and false.

•In C we use integers as Booleans.

•0 represents false.

•Any !=0 integer represents true.

•Έχετε δοκιμάσει x==-1;

Arrays (1D)

•All the elements are of the same type.

•An element: array1D[index]

•In C, the first element has index 0 (zero).

array1D:

0 1 N - 1

Strings : array of characters

char name[30]; Example:

Unlike other arrays,

strings require an end-of-string character : ‘\0’

max length

including ‘\0’

Multidimensional Arrays

•All the elements are of the same type.

•An element: array2D[row][column]

array2D:

#include <stdio.h>

int leapYear(int year)

{

if ((year % 4 == 0 && year % 100 != 0))

|| (year % 400 == 0) )

{

return 1;

}

else

{

return 0;

}

}

Example 1:

#include <stdio.h>

int leapYear(int year)

{

if ((year % 4 == 0 && year % 100 != 0))

|| (year % 400 == 0) )

{

return 1;

}

else

{

return 0;

}

}

File inclusion header

#include <stdio.h>

int leapYear(int year)

{

if ((year % 4 == 0 && year % 100 != 0))

|| (year % 400 == 0) )

{

return 1;

}

else

{

return 0;

}

}

Function definition

Function name #include <stdio.h>

int leapYear(int year)

{

if ((year % 4 == 0 && year % 100 != 0))

|| (year % 400 == 0) )

{

return 1;

}

else

{

return 0;

}

}

Must be compatible with the function’s return type

Function return type

#include <stdio.h>

int leapYear(int year)

{

if ((year % 4 == 0 && year % 100 != 0))

|| (year % 400 == 0) )

{

return 1;

}

else

{

return 0;

}

}

#include <stdio.h>

int leapYear(int year)

{

if ((year % 4 == 0 && year % 100 != 0))

|| (year % 400 == 0) )

{

return 1;

}

else

{

return 0;

}

}

Parameter type

Function parameter

#include <stdio.h>

int leapYear(int year)

{

if ((year % 4 == 0 && year % 100 != 0))

|| (year % 400 == 0) )

{

return 1;

}

else

{

return 0;

}

}

Example 1

int dayTable[2][13] = {

{0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31},

{0, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}

};

int dayOfYear(int year, int month, int day)

{

int i;

int isLeap = leapYear(year);

for (i = 1; i < month; i++) {

day += dayTable[isLeap][i];

}

return day;

}

Example 2

Global variable

Local variable

int dayTable[2][13] = {

{0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31},

{0, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}

};

int dayOfYear(int year, int month, int day)

{

int i;

int isLeap = leapYear(year);

for (i = 1; i < month; i++) {

day += dayTable[isLeap][i];

}

return day;

}

2-dimensional array of int

int dayTable[2][13] = {

{0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31},

{0, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}

};

int dayOfYear(int year, int month, int day)

{

int i;

int isLeap = leapYear(year);

for (i = 1; i < month; i++) {

day += dayTable[isLeap][i];

}

return day;

}

int dayTable[2][13] = {

{0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31},

{0, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}

};

int dayOfYear(int year, int month, int day)

{

int i;

int isLeap = leapYear(year);

for (i = 1; i < month; i++) {

day += dayTable[isLeap][i];

}

return day;

}

int dayTable[2][13] = {

{0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31},

{0, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}

};

int dayOfYear(int year, int month, int day)

{

int i;

int isLeap = leapYear(year);

for (i = 1; i < month; i++) {

day += dayTable[isLeap][i];

}

return day;

}

Example 2

main()

{

int year, month, day;

printf(“Enter year, month and day: ”);

scanf(“%d %d %d”, &year, &month, &day);

day = dayOfYear(year, month, day);

printf(“\nDay of Year = %d\n”, day);

}

Example 2 (main)

main()

{

int year, month, day;

printf(“Enter year, month and day: ”);

scanf(“%d %d %d”, &year, &month, &day);

day = dayOfYear(year, month, day);

printf(“\nDay of Year = %d\n”, day);

}

Function call

Struct (δομή)

•Members may have different types.

structure.member1

•structs are also known as “records” (εγγραφές) and members as

“fields”(πεδία)

Structure Name

member3

member4

member2

member1 (μέλος)

typedef

•Gives a new name to a type that has already

been defined.

•E.g.

typedef int Boolean;

•Saves typing struct SomeRec everywhere.

#include <stdio.h>

#define MAXNAME 80

struct StudentRec

{

char name[MAXNAME];

int mark;

};

typedef struct StudentRec Student;

Example 3:

Macro substitution

#include <stdio.h>

#define MAXNAME 80

struct StudentRec

{

char name[MAXNAME];

int mark;

};

typedef struct StudentRec Student;

#include <stdio.h>

#define MAXNAME 80

struct StudentRec

{

char name[MAXNAME];

int mark;

};

typedef struct StudentRec Student;

Structure declaration

Structure name / tag

Members

Don’t forget this!

#include <stdio.h>

#define MAXNAME 80

struct StudentRec

{

char name[MAXNAME];

int mark;

};

typedef struct StudentRec Student;

Data type

New type name

#include <stdio.h>

#define MAXNAME 80

struct StudentRec

{

char name[MAXNAME];

int mark;

};

typedef struct StudentRec Student;

Student readStudent(void)

{ Student next;

scanf(“%s %d”, next.name, &next.mark);

return next;

}

/* next.name without & */

void printStudent(const Student student)

{

printf(“%s %d\n”, student.name, student.mark);

}

An instance of the struct

A member of a struct variable “Package”

Student readStudent(void)

{ Student next;

scanf(“%s %d”, next.name, &next.mark);

return next;

}

void printStudent(const Student student)

{

printf(“%s %d\n”, student.name, student.mark);

}

#define MAXCLASS 100

main()

{

Student class[MAXCLASS];

int n, i, best = 0;

printf(“Enter number of students: ”);

scanf(“%d”, &n);

for (i = 0; i < n; i++) {

class[i] = readStudent();

if (class[best].mark < class[i].mark) {

best = i;

}

}

printf(“Best student is: ”);

printStudent(class[best]);

}

Array of instances of structs

Assignment

Member of an array element

#define MAXCLASS 100

main()

{

Student class[MAXCLASS];

int n, i, best = 0;

printf(“Enter number of students: ”);

scanf(“%d”, &n);

for (i = 0; i < n; i++) {

class[i] = readStudent();

if (class[best].mark < class[i].mark) {

best = i;

}

}

printf(“Best student is: ”);

printStudent(class[best]);

}