Entering APL Symbols (2 of 14)
APL uses a variety of symbols to represent its built-in functions. Many of these are symbols that do not exist on a standard keyboard. Some of these will be familiar (for example, ÷ for divide, and ≥ for greater-than-or-equal). Others are specific to APL (for example ⌈ for round-up or greater-of, and ≡ for finding out if two arrays are exactly the same in shape and contents).
In order to use APL, you need to be able to enter these symbols.
The exact way of doing so will vary from one APL to another, so the following is only a guide. You should consult the documentation which comes with your version of APL.
Choosing the keyboard layout
Two APL keyboard layouts are quite commonly used, and some APLs support both:
The Unified APL layout, as shown above. This is similar to an ordinary ASCII keyboard layout for unshifted and shifted keys. Special APL symbols are obtained by using !Alt or Shift-!Alt combinations. If you are learning APL we recommend that you use this layout if available.
The Standard or Traditional APL layout. This is based on the traditional APL keyboard where alphabetic keys unshifted give upper-case letters, shifted give APL symbols, and with the Alt key give lower-case letters. It is recommended only for people who are used to programming in APL using a special APL keyboard.
Within these two schemes your APL may also let you choose between different language versions, for example a keyboard layout including all the characters needed to type Danish or French.
Suggestion: If you are learning the APL keyboard, you should check whether your APL includes an on-screen keyboard which you can display for reference purposes.
Other ways of entering APL
Some APLs also include facilities to enter APL characters by choosing from a palette of symbols on screen.