Variabel tidak lain adalah untuk menyimpan data pada program kita sehingga program dapat memanipulasi data tersebut. Variabel akan menyimpan tipe data berdasarkan besar ukuran dan layout memori. Berikut adalah daftar kategori dan tipe data dalam C#:
| Type | Example |
|---|---|
| Integral types | sbyte, byte, short, ushort, int, uint, long, ulong, and char |
| Floating point types | float and double |
| Decimal types | decimal |
| Boolean types | true or false values, as assigned |
| Nullable types | Nullable data types |
Selain tipe data diatas juga terdapat tipe data enum dan class tetapi tidak akan kita bahas dalam bab ini guys.
Mendefinisikan Variabel
Untuk mendefinisikan variable dalam C# menggunakan format syntax sebagai berikut:
<data_type> <variable_list>;
data_type merupakan tipe data yang valid dalam C#, termasuk int, char, float, double atau tipe yang lain. Sedangkan variable_list merupakan nama dari variabel yang dipisahkan dengan koma jika lebih dari satu.
Contoh:
int i, j, k; char c, ch; float f, salary; double d;
Kita dapat menginisialisasi nilai variabel dengan cara:
int i = 100;
Menginisialisasi Variabel
Menginisialisasi variabel atau bahasa gampangnya mengisi variabel dengan suatu nilai adalah dengan menggunakan tanda samadengan (=) kemudian diikuti dengan nilai yang akan di masukkan. Format untuk inisialisasi variabel adalah sebagai berikut:
variable_name = value;
Variabel juga bisa diinisalisasi ketika mendeklarasikan variabel tersebut, dengan format sebagai berikut:
<data_type> <variable_name> = value;
sebagai contoh:
int d = 3, f = 5; /* menginisialisasi d and f. */ byte z = 22; /* menginisialisasi z. */ double pi = 3.14159; /* mendeklarasikan nilai pi. */ char x = 'x'; /* mengisi nilai dengan karakter 'x'. */
berikut adalah contoh program untuk mensimulasikan inisialisasi variabel:
using System;
namespace VariableDefinition
{
class Program
{
static void Main(string[] args)
{
short a;
int b ;
double c;
/* actual initialization */
a = 10;
b = 20;
c = a + b;
Console.WriteLine("a = {0}, b = {1}, c = {2}", a, b, c);
Console.ReadLine();
}
}
}
setelah program dijalankan akan memberikan keluaran sebagai berikut:
a = 10, b = 20, c = 30
Menerima Masukan Dari User kemudian diisikan ke dalam Variabel
Dalam library C# terdapat fungsi Readline di dalam class Console tepatnya di dalam System.Console.Readline(). Yang dapat digunakan untuk mendapatkan input dari user untuk mengisi nilai variabel.
sebagai contoh:
int num; num = Convert.ToInt32(Console.ReadLine());
kita perlu mengkonversi input dari user berupa kedalam tipe int, karena tipe dari variabel num adalah int. Yang perlu diingat adalah hasil dari Console.Readline() adalah sebuah string.
2. Konstanta
Konstanta adalah sebuah nilai yang tidak dapat diubah, konstanta berisi tipe data yang valida dalam bahasa pemrograman, seperti int, float, string atau class. Nilai yang tidak dapat diubah ubah ini sering disebut sebagai literals.
Konstanta sebenernya sama dengan varibel hanya saja nilainya tidak dapat diubah ubah.
Integer Literals
Integer literals dapat berupa konstanta desimal atau hexadesimal. Awalan pada pendefinisian akan menunjukkan apakah itu desimal atau hexadesimal. Untuk hexadesimal akan diawali dengan 0x atau 0X, sedangkan untuk nilai desimal tidak ada awalan pada saat pendefinisian.
Integer literals juga bisa memiliki akhiran untuk mendefinisikan tipe data, misalnya U dan L untuk mendefinisikan Unsigned Long. Akhiran ini bisa dalam huruf besar atau kecil.
berikut adalah contoh integer literals:
212 /* Legal */ 215u /* Legal */ 0xFeeL /* Legal */ 85 /* decimal */ 0x4b /* hexadecimal */ 30 /* int */ 30u /* unsigned int */ 30l /* long */ 30ul /* unsigned long */
Floating Point Literals
Floating point literals terdiri dari integer, desimal, pecahan dan juga perpangkatan atau eksponensial. Kita dapat mendefinisikan floating point dengan menggunakan desimal atau eksponensial.
berikut contoh ekspresi untuk floating point literals:
3.14159 /* Legal */ 314159E-5L /* Legal */ 510E /* Illegal: incomplete exponent */ 210f /* Illegal: no decimal or exponent */ .e55 /* Illegal: missing integer or fraction */
Character Literals
Karakter literals menggunakan single quote 'x' untuk meninisialisasi nilai. Dapat berupa karanter murni seperti 'a', 'b', 'z'. Berupa escape sequence '\t', '\n', '\r' atau universal karakter seperti '\u02C0'.
Seperti pada bahasa pemrograman umumnya escape sequence memiliki arti dalam C#:
| Escape sequence | Meaning |
|---|---|
| \\ | \ character |
| \' | ' character |
| \" | " character |
| \? | ? character |
| \a | Alert or bell |
| \b | Backspace |
| \f | Form feed |
| \n | Newline |
| \r | Carriage return |
| \t | Horizontal tab |
| \v | Vertical tab |
| \xhh . . . | Hexadecimal number of one or more digits |
using System;
namespace EscapeChar
{
class Program
{
static void Main(string[] args)
{
Console.WriteLine("Hello\tWorld\n\n");
Console.ReadLine();
}
}
}
Setelah program dijalankan akan memberikan output:
Hello World
String Literals
String literals ditandai dengan double quote "" atau @"". String literals terdiri dari urutan karakter bisa berupa plain, escape sequence atau universal character.
Kita dapat memecah string yang panjang menjadi beberapa baris dengan menggunakan whitespaces.
Berkut adalah contoh pendefinisian string literals:
"hello, dear" "hello, \ dear" "hello, " "d" "ear" @"hello dear"
Mendefinisikan Konstanta
Konstanta didefinisikan dengan menggunakan keyword const, syntax untuk mendefinisikan konstanta adalah sebagai berikut:
const <data_type> <constant_name> = value;
Berikut adalah contoh program untuk mensimulasikan konstanta:
using System;
namespace DeclaringConstants
{
class Program
{
static void Main(string[] args)
{
const double pi = 3.14159;
// constant declaration
double r;
Console.WriteLine("Enter Radius: ");
r = Convert.ToDouble(Console.ReadLine());
double areaCircle = pi * r * r;
Console.WriteLine("Radius: {0}, Area: {1}", r, areaCircle);
Console.ReadLine();
}
}
}
Ketika program dijalankan akan memberikan hasil sebagai berikut:
Enter Radius: 3 Radius: 3, Area: 28.27431
3. Operator
Operator adalah simbol untuk memberitahukan kedapada compiler untuk menjalankan operasi metematika atau manipulasi logika. Semua bahasa pemrograman sudah pasti punya built-in operator, berikut adalah built-in operator pada C#:
- Arithmetic Operators
- Relational Operators
- Logical Operators
- Bitwise Operators
- Assignment Operators
- Misc Operators
Arithmetic Operators
Berikut adalah arithmetic operator yang ada dalam C#, sebagai contoh variabel A berisi nilai 10 dan variabel B berisi nilai 20.
| Operator | Description | Example |
|---|---|---|
| + | Adds two operands | A + B = 30 |
| - | Subtracts second operand from the first | A - B = -10 |
| * | Multiplies both operands | A * B = 200 |
| / | Divides numerator by de-numerator | B / A = 2 |
| % | Modulus Operator and remainder of after an integer division | B % A = 0 |
| ++ | Increment operator increases integer value by one | A++ = 11 |
| -- | Decrement operator decreases integer value by one | A-- = 9 |
using System;
namespace OperatorsAppl
{
class Program
{
static void Main(string[] args)
{
int a = 21;
int b = 10;
int c;
c = a + b;
Console.WriteLine("Line 1 - Value of c is {0}", c);
c = a - b;
Console.WriteLine("Line 2 - Value of c is {0}", c);
c = a * b;
Console.WriteLine("Line 3 - Value of c is {0}", c);
c = a / b;
Console.WriteLine("Line 4 - Value of c is {0}", c);
c = a % b;
Console.WriteLine("Line 5 - Value of c is {0}", c);
c = a++;
Console.WriteLine("Line 6 - Value of c is {0}", c);
c = a--;
Console.WriteLine("Line 7 - Value of c is {0}", c);
Console.ReadLine();
}
}
}
Hasil keluaran program ketika dijalankan:
Line 1 - Value of c is 31 Line 2 - Value of c is 11 Line 3 - Value of c is 210 Line 4 - Value of c is 2 Line 5 - Value of c is 1 Line 6 - Value of c is 22 Line 7 - Value of c is 20
Relational Operators
Tabel berikut memnunjukkan relational operators yang disuport oleh C#, kita asumsikan kalau variabel A bernilai 10 dan variable B bernilai 20.
| Operator | Description | Example |
|---|---|---|
| == | Checks if the values of two operands are equal or not, if yes then condition becomes true. | (A == B) is not true. |
| != | Checks if the values of two operands are equal or not, if values are not equal then condition becomes true. | (A != B) is true. |
| > | Checks if the value of left operand is greater than the value of right operand, if yes then condition becomes true. | (A > B) is not true. |
| < | Checks if the value of left operand is less than the value of right operand, if yes then condition becomes true. | (A < B) is true. |
| >= | Checks if the value of left operand is greater than or equal to the value of right operand, if yes then condition becomes true. | (A >= B) is not true. |
| <= | Checks if the value of left operand is less than or equal to the value of right operand, if yes then condition becomes true. | (A <= B) is true. |
using System;
class Program
{
static void Main(string[] args)
{
int a = 21;
int b = 10;
if (a == b)
{
Console.WriteLine("Line 1 - a is equal to b");
}
else
{
Console.WriteLine("Line 1 - a is not equal to b");
}
if (a < b)
{
Console.WriteLine("Line 2 - a is less than b");
}
else
{
Console.WriteLine("Line 2 - a is not less than b");
}
if (a > b)
{
Console.WriteLine("Line 3 - a is greater than b");
}
else
{
Console.WriteLine("Line 3 - a is not greater than b");
}
/* Lets change value of a and b */
a = 5;
b = 20;
if (a <= b)
{
Console.WriteLine("Line 4 - a is either less than or equal to b");
}
if (b >= a)
{
Console.WriteLine("Line 5-b is either greater than or equal to b");
}
}
}
Ketika program dijalankan akan memberikan hasil sebagai berikut:
Line 1 - a is not equal to b Line 2 - a is not less than b Line 3 - a is greater than b Line 4 - a is either less than or equal to b Line 5 - b is either greater than or equal to b
Logical Operators
Digunakan untuk melakukan operasi logik, kita asumsikan A berniai boolean true sedangkan B bernilai boolean false. Untuk tabel pembuktian adalah sebagai berikut:
| Operator | Description | Example |
|---|---|---|
| && | Called Logical AND operator. If both the operands are non zero then condition becomes true. | (A && B) is false. |
| || | Called Logical OR Operator. If any of the two operands is non zero then condition becomes true. | (A || B) is true. |
| ! | Called Logical NOT Operator. Use to reverses the logical state of its operand. If a condition is true then Logical NOT operator will make false. | !(A && B) is true. |
using System;
namespace OperatorsAppl
{
class Program
{
static void Main(string[] args)
{
bool a = true;
bool b = true;
if (a && b)
{
Console.WriteLine("Line 1 - Condition is true");
}
if (a || b)
{
Console.WriteLine("Line 2 - Condition is true");
}
/* lets change the value of a and b */
a = false;
b = true;
if (a && b)
{
Console.WriteLine("Line 3 - Condition is true");
}
else
{
Console.WriteLine("Line 3 - Condition is not true");
}
if (!(a && b))
{
Console.WriteLine("Line 4 - Condition is true");
}
Console.ReadLine();
}
}
}
Keluaran program adalah sebagai berikut:
Line 1 - Condition is true Line 2 - Condition is true Line 3 - Condition is not true Line 4 - Condition is true
Bitwise Operators
Operasi bitwise adalah operasi logical tetapi dilakukan pada level bit per bit. Tabel kebenaran untuk operasi & (AND), | (OR) dan ^ (XOR).
| p | q | p & q | p | q | p ^ q |
|---|---|---|---|---|
| 0 | 0 | 0 | 0 | 0 |
| 0 | 1 | 0 | 1 | 1 |
| 1 | 1 | 1 | 1 | 0 |
| 1 | 0 | 0 | 1 | 1 |
A = 0011 1100
B = 0000 1101
-----------------
A&B = 0000 1100
A|B = 0011 1101
A^B = 0011 0001
~A = 1100 0011
Tabel dibawah ini akan menunjukkan tabel untuk operasi bitwise, dengan asumsi A = 60 dan B = 13.
| Operator | Description | Example |
|---|---|---|
| & | Binary AND Operator copies a bit to the result if it exists in both operands. | (A & B) = 12, which is 0000 1100 |
| | | Binary OR Operator copies a bit if it exists in either operand. | (A | B) = 61, which is 0011 1101 |
| ^ | Binary XOR Operator copies the bit if it is set in one operand but not both. | (A ^ B) = 49, which is 0011 0001 |
| ~ | Binary Ones Complement Operator is unary and has the effect of 'flipping' bits. | (~A ) = 61, which is 1100 0011 in 2's complement due to a signed binary number. |
| << | Binary Left Shift Operator. The left operands value is moved left by the number of bits specified by the right operand. | A << 2 = 240, which is 1111 0000 |
| >> | Binary Right Shift Operator. The left operands value is moved right by the number of bits specified by the right operand. | A >> 2 = 15, which is 0000 1111 |
using System;
namespace OperatorsAppl
{
class Program
{
static void Main(string[] args)
{
int a = 60; /* 60 = 0011 1100 */
int b = 13; /* 13 = 0000 1101 */
int c = 0;
c = a & b; /* 12 = 0000 1100 */
Console.WriteLine("Line 1 - Value of c is {0}", c );
c = a | b; /* 61 = 0011 1101 */
Console.WriteLine("Line 2 - Value of c is {0}", c);
c = a ^ b; /* 49 = 0011 0001 */
Console.WriteLine("Line 3 - Value of c is {0}", c);
c = ~a; /*-61 = 1100 0011 */
Console.WriteLine("Line 4 - Value of c is {0}", c);
c = a << 2; /* 240 = 1111 0000 */
Console.WriteLine("Line 5 - Value of c is {0}", c);
c = a >> 2; /* 15 = 0000 1111 */
Console.WriteLine("Line 6 - Value of c is {0}", c);
Console.ReadLine();
}
}
}
Keluaran program ketika dijalankan:
Line 1 - Value of c is 12 Line 2 - Value of c is 61 Line 3 - Value of c is 49 Line 4 - Value of c is -61 Line 5 - Value of c is 240 Line 6 - Value of c is 15
Assignment Operators
Tabel berikut menunjukkan assignment operator pada C#:
| Operator | Description | Example |
|---|---|---|
| = | Simple assignment operator, Assigns values from right side operands to left side operand | C = A + B assigns value of A + B into C |
| += | Add AND assignment operator, It adds right operand to the left operand and assign the result to left operand | C += A is equivalent to C = C + A |
| -= | Subtract AND assignment operator, It subtracts right operand from the left operand and assign the result to left operand | C -= A is equivalent to C = C - A |
| *= | Multiply AND assignment operator, It multiplies right operand with the left operand and assign the result to left operand | C *= A is equivalent to C = C * A |
| /= | Divide AND assignment operator, It divides left operand with the right operand and assign the result to left operand | C /= A is equivalent to C = C / A |
| %= | Modulus AND assignment operator, It takes modulus using two operands and assign the result to left operand | C %= A is equivalent to C = C % A |
| <<= | Left shift AND assignment operator | C <<= 2 is same as C = C << 2 |
| >>= | Right shift AND assignment operator | C >>= 2 is same as C = C >> 2 |
| &= | Bitwise AND assignment operator | C &= 2 is same as C = C & 2 |
| ^= | bitwise exclusive OR and assignment operator | C ^= 2 is same as C = C ^ 2 |
| |= | bitwise inclusive OR and assignment operator | C |= 2 is same as C = C | 2 |
using System;
namespace OperatorsAppl
{
class Program
{
static void Main(string[] args)
{
int a = 21;
int c;
c = a;
Console.WriteLine("Line 1 - = Value of c = {0}", c);
c += a;
Console.WriteLine("Line 2 - += Value of c = {0}", c);
c -= a;
Console.WriteLine("Line 3 - -= Value of c = {0}", c);
c *= a;
Console.WriteLine("Line 4 - *= Value of c = {0}", c);
c /= a;
Console.WriteLine("Line 5 - /= Value of c = {0}", c);
c = 200;
c %= a;
Console.WriteLine("Line 6 - %= Value of c = {0}", c);
c <<= 2;
Console.WriteLine("Line 7 - <<= Value of c = {0}", c);
c >>= 2;
Console.WriteLine("Line 8 - >>= Value of c = {0}", c);
c &= 2;
Console.WriteLine("Line 9 - &= Value of c = {0}", c);
c ^= 2;
Console.WriteLine("Line 10 - ^= Value of c = {0}", c);
c |= 2;
Console.WriteLine("Line 11 - |= Value of c = {0}", c);
Console.ReadLine();
}
}
}
Keluaran program setelah dijalankan:
Line 1 - = Value of c = 21 Line 2 - += Value of c = 42 Line 3 - -= Value of c = 21 Line 4 - *= Value of c = 441 Line 5 - /= Value of c = 21 Line 6 - %= Value of c = 11 Line 7 - <<= Value of c = 44 Line 8 - >>= Value of c = 11 Line 9 - &= Value of c = 2 Line 10 - ^= Value of c = 0 Line 11 - |= Value of c = 2
Operator Lain yang penting dalam C#:
| Operator | Description | Example |
|---|---|---|
| sizeof() | Returns the size of a data type. | sizeof(int), returns 4. |
| typeof() | Returns the type of a class. | typeof(StreamReader); |
| & | Returns the address of an variable. | &a; returns actual address of the variable. |
| * | Pointer to a variable. | *a; creates pointer named 'a' to a variable. |
| ? : | Conditional Expression | If Condition is true ? Then value X : Otherwise value Y |
| is | Determines whether an object is of a certain type. | If( Ford is Car) // checks if Ford is an object of the Car class. |
| as | Cast without raising an exception if the cast fails. | Object obj = new StringReader("Hello"); StringReader r = obj as StringReader; |
Berikut adalah contoh program untuk mensimulasikan operator diatas:
using System;
namespace OperatorsAppl
{
class Program
{
static void Main(string[] args)
{
/* example of sizeof operator */
Console.WriteLine("The size of int is {0}", sizeof(int));
Console.WriteLine("The size of short is {0}", sizeof(short));
Console.WriteLine("The size of double is {0}", sizeof(double));
/* example of ternary operator */
int a, b;
a = 10;
b = (a == 1) ? 20 : 30;
Console.WriteLine("Value of b is {0}", b);
b = (a == 10) ? 20 : 30;
Console.WriteLine("Value of b is {0}", b);
Console.ReadLine();
}
}
}
Berikut adalah keluaran program diatas jika dijalankan:
The size of int is 4 The size of short is 2 The size of double is 8 Value of b is 30 Value of b is 20
Urutan Prioritas Operasi Operator
Dalam pengoperasian operators mempunya urutan dan prioritas seperti halnya ketika kita belajar matematika di sekolah dasar. Misalnya ada ekpresi a = 2 + 4 * 2 - 5, maka operasi yang akan dilakukan terlebih dahulu adalah perkalian, kemudian penambahan baru kemudian pengurangan. Jika kita buat sebuah prioritas maka ekspresi tersebut akan menjadi a = ((2 + (4 * 2)) - 5).
Berikut adalah tabel untuk urutan prioritas operasi operator:
| Category | Operator | Associativity |
|---|---|---|
| Postfix | () [] -> . ++ - - | Left to right |
| Unary | + - ! ~ ++ - - (type)* & sizeof | Right to left |
| Multiplicative | * / % | Left to right |
| Additive | + - | Left to right |
| Shift | << >> | Left to right |
| Relational | < <= > >= | Left to right |
| Equality | == != | Left to right |
| Bitwise AND | & | Left to right |
| Bitwise XOR | ^ | Left to right |
| Bitwise OR | | | Left to right |
| Logical AND | && | Left to right |
| Logical OR | || | Left to right |
| Conditional | ?: | Right to left |
| Assignment | = += -= *= /= %=>>= <<= &= ^= |= | Right to left |
| Comma | , | Left to right |
using System;
namespace OperatorsAppl
{
class Program
{
static void Main(string[] args)
{
int a = 20;
int b = 10;
int c = 15;
int d = 5;
int e;
e = (a + b) * c / d; // ( 30 * 15 ) / 5
Console.WriteLine("Value of (a + b) * c / d is : {0}", e);
e = ((a + b) * c) / d; // (30 * 15 ) / 5
Console.WriteLine("Value of ((a + b) * c) / d is : {0}", e);
e = (a + b) * (c / d); // (30) * (15/5)
Console.WriteLine("Value of (a + b) * (c / d) is : {0}", e);
e = a + (b * c) / d; // 20 + (150/5)
Console.WriteLine("Value of a + (b * c) / d is : {0}", e);
Console.ReadLine();
}
}
}
Berikut adalah keluaran program setelah dijalankan:
Value of (a + b) * c / d is : 90 Value of ((a + b) * c) / d is : 90 Value of (a + b) * (c / d) is : 90 Value of a + (b * c) / d is : 50
Ok guys sampai ketemu di tutorial selanjutnya Pengambilan Keputusan.
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