For a list of keyboard shortcuts see Table of keyboard shortcuts

Table of keyboard shortcuts

In computing, a keyboard shortcut is a sequence or combination of keystrokes on a computer keyboard which invokes commands in software.Some keyboard shortcuts require the user to press a single key or a sequence of keys one after the other. Other keyboard shortcuts require pressing and holding...

The Alt key on a computer keyboard is used to change (alternate) the function of other pressed keys. Thus, the Alt key is a modifier key

Modifier key

In computing, a modifier key is a special key on a computer keyboard that modifies the normal action of another key when the two are pressed in combination....

, used in a similar fashion to the Shift key

Shift key

The shift key is a modifier key on a keyboard, used to type capital letters and other alternate "upper" characters. There are typically two shift keys, on the left and right sides of the row below the home row...

. For example, simply pressing "A" will type the letter a, but if you hold down either Alt key while pressing A, the computer

Computer

A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...

 will perform an function, which varies from program

Computer program

A computer program is a sequence of instructions written to perform a specified task with a computer. A computer requires programs to function, typically executing the program's instructions in a central processor. The program has an executable form that the computer can use directly to execute...

 to program. In non-US keyboard layouts, rather than a second Alt key, there is an 'Alt Gr

AltGr key

AltGr is a modifier key found on many computer keyboards and primarily used to type characters that are unusual for the locale of the keyboard layout, such as currency symbols and accented letters...

' key to the right of the space bar. The key is located immediately to either side of the Space bar

Space bar

thumb|250px|A [[computer keyboard]], Space Bar is on the bottom center of the keyboardThe space bar, spacebar, or space key, is a key on an alphanumeric keyboard in the form of a horizontal bar in the lowermost row, significantly wider than other keys. Its main purpose is to conveniently enter the...

. Some keyboard layouts treat both Alt keys on the keyboard as the same key, while others do not.

Evolution

The Alt key has come to replace the Meta key

Meta key

The meta key is a special key on MIT keyboards, such as the space-cadet keyboard, and on Sun Microsystems keyboards, marked as a solid diamond.The key is similar in function to the Macintosh's command key, which has the same location...

 of the old MIT keyboards. In their original function, both Alt and Meta would set the high bit

Bit

A bit is the basic unit of information in computing and telecommunications; it is the amount of information stored by a digital device or other physical system that exists in one of two possible distinct states...

 of the signal generated by the key to 1 (for example, A generates 01000001 while generates 11000001). However, in modern software, due to the requirement of the high bit for internationalisation

Internationalization and localization

In computing, internationalization and localization are means of adapting computer software to different languages, regional differences and technical requirements of a target market...

, Alt no longer works in such a way.

Since the 1990s Alt has been printed on the Option key

Option key

The Option key is a modifier key present on Apple keyboards. It is located between the Control key and Command key on a typical Mac keyboard. There are two option keys on modern Mac desktop and notebook keyboards, one on each side of the space bar....

 on most Mac keyboards. Alt is used in non-Mac software, such as Unix and Windows programs, but in OS X it is always referred as Option key. Option key's behaviour in Mac OS X differs slightly from that of the Windows Alt key (it is used as a modifier rather than to access pull-down menus, for example).

Alt key combinations

The Alt key is well known as part of the Control-Alt-Delete

Control-Alt-Delete

Control-Alt-Delete is a computer keyboard command on IBM PC compatible systems that can be used to reboot the computer, and summon the task manager or Windows Security in more recent versions of the Microsoft Windows operating system...

 key combination, which in some operating systems brings up the task manager

Task manager

A task manager is a program used to provide information about the processes and programs running on a computer, as well as the general status of the computer. It can also be used to terminate processes and programs, as well as change the processes priority...

. The X Window System

X Window System

The X window system is a computer software system and network protocol that provides a basis for graphical user interfaces and rich input device capability for networked computers...

 also uses Control-Alt-Backspace, which usually causes the X server to shut down or restart.

Other well-known combinations which the Alt key is part of include Alt-F4, to close a window, and Alt-Tab

Alt-Tab

' is the common name for a keyboard shortcut that has been in Microsoft Windows since Windows 3.0. This shortcut switches between top-level windows without using the mouse; hence it was named Task Switcher ....

, to switch between windows. Additionally, in many traditional GUI

Gui

Gui or guee is a generic term to refer to grilled dishes in Korean cuisine. These most commonly have meat or fish as their primary ingredient, but may in some cases also comprise grilled vegetables or other vegetarian ingredients. The term derives from the verb, "gupda" in Korean, which literally...

 environments, including Microsoft Windows, Alt is used to access pull-down menus.

Windows

In Microsoft Windows

Microsoft Windows

Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...

, holding down the Alt key while typing in numbers (often referred to as Alt codes

Alt codes

On personal computers running the Microsoft Windows or DOS operating systems, additional characters to those available in the current keyboard layout can be typed using an Alt code: pressing and holding the Alt key while entering a character code with the keyboard's numeric keypad...

) on the numeric keypad allows the user to type special characters not normally available on the keyboard. For example, holding down Alt while typing 0225 on the numeric keypad will result in á, the character at 225 in the codepage. These extended keyboard characters are useful for persons using foreign languages, mathematics, currency symbols, business use, etc. It is important to make sure the Num Lock key is on.

Mac OS X

On a Macintosh

Macintosh

The Macintosh , or Mac, is a series of several lines of personal computers designed, developed, and marketed by Apple Inc. The first Macintosh was introduced by Apple's then-chairman Steve Jobs on January 24, 1984; it was the first commercially successful personal computer to feature a mouse and a...

, the Alt key is called the Option key

Option key

The Option key is a modifier key present on Apple keyboards. It is located between the Control key and Command key on a typical Mac keyboard. There are two option keys on modern Mac desktop and notebook keyboards, one on each side of the space bar....

. It is not used to enter numeric character codes. Instead, keyboard letters and numbers are used. The diagram below shows the special characters a US Mac keyboard will produce when the Option key is pressed.
The highlighted orange keys show the accents available from the combination of the key and the keyboard characters . The accent then can be applied to associated letters both lower and uppercase. The additional characters a Mac will produce are a combination of both the key and the key pressed down together. With this combination pressed the keyboard will now produce a different set or an uppercase version of the previous set in some cases.