# about_Arithmetic_Operators

## Short description

Describes the operators that perform arithmetic in PowerShell.

## Long description

Arithmetic operators calculate numeric values. You can use one or more arithmetic operators to add, subtract, multiply, and divide values, and to calculate the remainder (modulus) of a division operation.

The addition operator (`+`

) and multiplication operator (`*`

) also operate on
strings, arrays, and hashtables. The addition operator concatenates the input.
The multiplication operator returns multiple copies of the input. You can even
mix object types in an arithmetic statement. The method that's used to evaluate
the statement is determined by the type of the leftmost object in the
expression.

Beginning in PowerShell 2.0, all arithmetic operators work on 64-bit numbers.

Beginning in PowerShell 3.0, the `-shr`

(shift-right) and `-shl`

(shift-left)
are added to support bitwise arithmetic in PowerShell. The bitwise operators
only work on integer types.

PowerShell supports the following arithmetic operators:

Addition (

`+`

) - Adds numbers, concatenates strings, arrays, and hash tables`6 + 2 # result = 8 "file" + "name" # result = "filename" @(1, "one") + @(2.0, "two") # result = @(1, "one", 2.0, "two") @{"one" = 1} + @{"two" = 2} # result = @{"one" = 1; "two" = 2}`

Subtraction (

`-`

) - Subtracts or negates numbers`6 - 2 # result = 4 - -6 # result = 6 (Get-Date).AddDays(-1) # Yesterday's date`

Multiplication (

`*`

) - Multiply numbers or copy strings and arrays the specified number of times`6 * 2 # result = 12 @("!") * 4 # result = @("!","!","!","!") "!" * 3 # result = "!!!"`

Division (

`/`

) - Divides numbers`6 / 2 # result = 3`

Modulus (

`%`

) - returns the remainder of a division operation.`7 % 2 # result = 1`

Bitwise AND (

`-band`

)`5 -band 3 # result = 1`

Bitwise NOT (

`-bnot`

)`-bnot 5 # result = -6`

Bitwise OR (

`-bor`

)`5 -bor 0x03 # result = 7`

Bitwise XOR (

`-bxor`

)`5 -bxor 3 # result = 6`

Shifts bits to the left (

`-shl`

)`102 -shl 2 # result = 408`

Shifts bits to the right (

`-shr`

)`102 -shr 2 # result = 25`

## Operator precedence

PowerShell processes arithmetic operators in the following order:

Precedence | Operator | Description |
---|---|---|

1 | `()` |
Parentheses |

2 | `-` |
For a negative number or unary operator |

3 | `*` , `/` , `%` |
For multiplication and division |

4 | `+` , `-` |
For addition and subtraction |

5 | `-band` , `-bnot` |
For bitwise operations |

5 | `-bor` , `-bxor` |
For bitwise operations |

5 | `-shr` , `-shl` |
For bitwise operations |

PowerShell processes the expressions from left to right according to the precedence rules. The following examples show the effect of the precedence rules:

```
3+6/3*4 # result = 11
3+6/(3*4) # result = 3.5
(3+6)/3*4 # result = 12
```

The order in which PowerShell evaluates expressions might differ from other programming and scripting languages that you have used. The following example shows a complicated assignment statement.

```
$a = 0
$b = @(1,2)
$c = @(-1,-2)
$b[$a] = $c[$a++]
```

In this example, the expression `$a++`

is evaluated before `$b[$a]`

. Evaluating
`$a++`

changes the value of `$a`

after it's used in the statement `$c[$a++]`

,
but before it's used in `$b[$a]`

. The variable `$a`

in `$b[$a]`

equals `1`

, not
`0`

. Therefore, the statement assigns a value to `$b[1]`

, not `$b[0]`

.

The code above is equivalent to:

```
$a = 0
$b = @(1,2)
$c = @(-1,-2)
$tmp = $c[$a]
$a = $a + 1
$b[$a] = $tmp
```

## Division and rounding

When the quotient of a division operation is an integer, PowerShell rounds the
value to the nearest integer. When the value is `.5`

, it rounds to the nearest
even integer.

The following example shows the effect of rounding to the nearest even integer.

```
PS> [int]( 5 / 2 ) # Result is rounded down
2
PS> [int]( 7 / 2 ) # Result is rounded up
4
```

You can use the `[Math]`

class to get different rounding behavior.

```
PS> [int][Math]::Round(5 / 2,[MidpointRounding]::AwayFromZero
3
PS> [int][Math]::Ceiling(5 / 2)
3
PS> [int][Math]::Floor(5 / 2)
2
```

For more information, see the Math.Round method.

## Adding and multiplying non numeric types

You can add numbers, strings, arrays, and hash tables. And, you can multiply numbers, strings, and arrays. However, you can't multiply hash tables.

When you add strings, arrays, or hash tables, the elements are concatenated. When you concatenate collections, such as arrays or hash tables, a new object is created that contains the objects from both collections. If you try to concatenate hash tables that have the same key, the operation fails.

For example, the following commands create two arrays and then add them:

```
$a = 1,2,3
$b = "A","B","C"
$a + $b
```

```
1
2
3
A
B
C
```

You can also perform arithmetic operations on objects of different types. The operation that PowerShell performs is determined by the Microsoft .NET type of the leftmost object in the operation. PowerShell tries to convert all the objects in the operation to the .NET type of the first object. If it succeeds in converting the objects, it performs the operation appropriate to the .NET type of the first object. If it fails to convert any of the objects, the operation fails.

The following examples demonstrate the use of the addition and multiplication operators in operations that include different object types.

```
$array = 1,2,3
$red = [ConsoleColor]::Red
$blue = [ConsoleColor]::Blue
"file" + 16 # result = "file16"
$array + 16 # result = 1,2,3,16
$array + "file" # result = 1,2,3,"file"
$array * 2 # result = 1,2,3,1,2,3
"file" * 3 # result = "filefilefile"
$blue + 3 # result = Red
$red - 3 # result = Blue
$blue - $red # result = -3
+ '123' # result = 123
```

Because the method that's used to evaluate statements is determined by the
leftmost object, addition and multiplication in PowerShell aren't strictly
commutative. For example, `(a + b)`

doesn't always equal `(b + a)`

, and `(ab)`

doesn't always equal `(ba)`

.

The following examples demonstrate this principle:

```
PS> "file" + 16
file16
PS> 16 + "file"
InvalidArgument: can't convert value "file" to type "System.Int32". Error:
"Input string wasn't in a correct format."
```

Hash tables are a slightly different case. You can add hash tables to another hash table, as long as, the added hash tables don't have duplicate keys.

The following example show how to add hash tables to each other.

```
$hash1 = @{a=1; b=2; c=3}
$hash2 = @{c1="Server01"; c2="Server02"}
$hash1 + $hash2
```

```
Name Value
---- -----
c2 Server02
a 1
b 2
c1 Server01
c 3
```

The following example throws an error because one of the keys is duplicated in both hash tables.

```
$hash1 = @{a=1; b=2; c=3}
$hash2 = @{c1="Server01"; c="Server02"}
$hash1 + $hash2
```

```
OperationStopped:
Line |
3 | $hash1 + $hash2
| ~~~~~~~~~~~~~~~
| Item has already been added. Key in dictionary: 'c' Key being added: 'c'
```

Also, you can add a hash table to an array; and, the entire hash table becomes an item in the array.

```
$array1 = @(0, "Hello World", [datetime]::Now)
$hash1 = @{a=1; b=2}
$array2 = $array1 + $hash1
$array2
```

```
0
Hello World
Monday, June 12, 2017 3:05:46 PM
Key : a
Value : 1
Name : a
Key : b
Value : 2
Name : b
```

However, you can't add any other type to a hash table.

```
$hash1 + 2
```

```
InvalidOperation: A hash table can only be added to another hash table.
```

Although the addition operators are very useful, use the assignment operators
to add elements to hash tables and arrays. For more information see
about_assignment_operators. The following
examples use the `+=`

assignment operator to add items to an array:

```
$array = @()
(0..9).foreach{ $array += $_ }
$array
```

```
0
1
2
```

## Type conversion to accommodate result

PowerShell automatically selects the .NET numeric type that best expresses the result without losing precision. For example:

```
2 + 3.1
(2).GetType().FullName
(2 + 3.1).GetType().FullName
```

```
5.1
System.Int32
System.Double
```

If the result of an operation is too large for the type, the type of the result is widened to accommodate the result, as in the following example:

```
(512MB).GetType().FullName
(512MB * 512MB).GetType().FullName
```

```
System.Int32
System.Double
```

The type of the result isn't always the same as one of the operands. In the
following example, the negative value can't be cast to an unsigned integer, and
the unsigned integer is too large to be cast to `Int32`

:

```
([int32]::minvalue + [uint32]::maxvalue).gettype().fullname
```

```
System.Int64
```

In this example, `Int64`

can accommodate both types.

The `System.Decimal`

type is an exception. If either operand has the
**Decimal** type, the result is **Decimal** type. Any result too large for the
**Decimal** value is an error.

```
PS> [Decimal]::maxvalue
79228162514264337593543950335
PS> [Decimal]::maxvalue + 1
RuntimeException: Value was either too large or too small for a Decimal.
```

## Arithmetic operators and variables

You can also use arithmetic operators with variables. The operators act on the values of the variables. The following examples demonstrate the use of arithmetic operators with variables:

```
PS> $intA = 6
PS> $intB = 4
PS> $intA + $intB
10
PS> $a = "Power"
PS> $b = "Shell"
PS> $a + $b
PowerShell
```

## Arithmetic operators and commands

Typically, you use the arithmetic operators in expressions with numbers, strings, and arrays. However, you can also use arithmetic operators with the objects that commands return and with the properties of those objects.

The following examples show how to use the arithmetic operators in expressions with PowerShell commands:

```
(get-date) + (new-timespan -day 1)
```

The parenthesis operator forces the evaluation of the `Get-Date`

cmdlet and the
evaluation of the `New-TimeSpan -Day 1`

cmdlet expression, in that order. Both
results are then added using the `+`

operator.

```
Get-Process | Where-Object { ($_.ws * 2) -gt 50mb }
```

```
Handles NPM(K) PM(K) WS(K) VM(M) CPU(s) Id ProcessName
------- ------ ----- ----- ----- ------ -- -----------
1896 39 50968 30620 264 1,572.55 1104 explorer
12802 78 188468 81032 753 3,676.39 5676 OUTLOOK
660 9 36168 26956 143 12.20 988 PowerShell
561 14 6592 28144 110 1,010.09 496 services
3476 80 34664 26092 234 ...45.69 876 svchost
967 30 58804 59496 416 930.97 2508 WINWORD
```

In the above expression, each process working space (`$_.ws`

) is multiplied by
`2`

; and, the result, compared against `50mb`

to see if it's greater than that.

## Bitwise operators

PowerShell supports the standard bitwise operators, including bitwise-AND
(`-band`

), the inclusive and exclusive bitwise-OR operators (`-bor`

and
`-bxor`

), and bitwise-NOT (`-bnot`

).

Beginning in PowerShell 2.0, all bitwise operators work with 64-bit integers.

Beginning in PowerShell 3.0, the `-shr`

(shift-right) and `-shl`

(shift-left)
are introduced to support bitwise arithmetic in PowerShell.

PowerShell supports the following bitwise operators.

Operator | Description | Expression | Result |
---|---|---|---|

`-band` |
Bitwise AND | `10 -band 3` |
2 |

`-bor` |
Bitwise OR (inclusive) | `10 -bor 3` |
11 |

`-bxor` |
Bitwise OR (exclusive) | `10 -bxor 3` |
9 |

`-bnot` |
Bitwise NOT | `-bNot 10` |
-11 |

`-shl` |
Shift-left | `102 -shl 2` |
408 |

`-shr` |
Shift-right | `102 -shr 1` |
51 |

Bitwise operators act on the binary format of a value. For example, the bit structure for the number 10 is 00001010 (based on 1 byte), and the bit structure for the number 3 is 00000011. When you use a bitwise operator to compare 10 to 3, the individual bits in each byte are compared.

In a bitwise AND operation, the resulting bit's set to 1 only when both input bits are 1.

```
1010 (10)
0011 ( 3)
-------------- bAND
0010 ( 2)
```

In a bitwise OR (inclusive) operation, the resulting bit's set to 1 when either or both input bits are 1. The resulting bit's set to 0 only when both input bits are set to 0.

```
1010 (10)
0011 ( 3)
-------------- bOR (inclusive)
1011 (11)
```

In a bitwise OR (exclusive) operation, the resulting bit's set to 1 only when one input bit's 1.

```
1010 (10)
0011 ( 3)
-------------- bXOR (exclusive)
1001 ( 9)
```

The bitwise NOT operator is a unary operator that produces the binary complement of the value. A bit of 1 is set to 0 and a bit of 0 is set to 1.

For example, the binary complement of 0 is -1, the maximum unsigned integer (0xffffffff), and the binary complement of -1 is 0.

```
-bNot 10
```

```
-11
```

```
0000 0000 0000 1010 (10)
------------------------- bNOT
1111 1111 1111 0101 (-11, xfffffff5)
```

In a bitwise shift-left operation, all bits are moved "n" places to the left, where "n" is the value of the right operand. A zero is inserted in the ones place.

When the left operand is an Integer (32-bit) value, the lower 5 bits of the right operand determine how many bits of the left operand are shifted.

When the left operand is a Long (64-bit) value, the lower 6 bits of the right operand determine how many bits of the left operand are shifted.

Expression | Result | Binary Result |
---|---|---|

`21 -shl 0` |
21 | 0001 0101 |

`21 -shl 1` |
42 | 0010 1010 |

`21 -shl 2` |
84 | 0101 0100 |

In a bitwise shift-right operation, all bits are moved "n" places to the right, where "n" is specified by the right operand. The shift-right operator (-shr) inserts a zero in the left-most place when shifting a positive or unsigned value to the right.

When the left operand is an Integer (32-bit) value, the lower 5 bits of the right operand determine how many bits of the left operand are shifted.

When the left operand is a Long (64-bit) value, the lower 6 bits of the right operand determine how many bits of the left operand are shifted.

Expression | Result | Binary | Hex |
---|---|---|---|

`21 -shr 0` |
21 | 0001 0101 | 0x15 |

`21 -shr 1` |
10 | 0000 1010 | 0x0A |

`21 -shr 2` |
5 | 0000 0101 | 0x05 |

`21 -shr 31` |
0 | 0000 0000 | 0x00 |

`21 -shr 32` |
21 | 0001 0101 | 0x15 |

`21 -shr 64` |
21 | 0001 0101 | 0x15 |

`21 -shr 65` |
10 | 0000 1010 | 0x0A |

`21 -shr 66` |
5 | 0000 0101 | 0x05 |

`[int]::MaxValue -shr 1` |
1073741823 | 0x3FFFFFFF | |

`[int]::MinValue -shr 1` |
-1073741824 | 0xC0000000 | |

`-1 -shr 1` |
-1 | 0xFFFFFFFF |

## See also

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