Guideline E: Input and output interfaces

E4: Capital lock & lock function



Supporting capital lock or level 2 lock function

One key, at the left end of row C of the keyboard layout shown in Guideline E1, is assigned to either the Level 2 Lock or Capitals Lock function. The Level 2 Lock function (sometimes known as the Shift Lock function) simply locks the keyboard into level 2, providing continuous access to the characters on the second level of the keyboard. The Capital Lock function on the other hand, produces only the uppercase version of the alphabetic characters. Since characters in some scripts are in one case only, the Capital Lock function may be inactive for some keys.

The Capital Lock and Level 2 Lock functions may seem to perform similar action, but they are actually quite different functions, with different national language implications. Each function offers convenience in some operations, and one or the other may be required by country standards.

The interaction of the Capital Lock and Level 2 Select functions is important to understand. Not all keyboards operate in the same way when these two functions are used together on keys where the lowercase and uppercase letters are on level 1 and 2 of the same key, respectively. Some implementations do not use the Level 2 Select key when Capital Lock is on. In other implementations, the Level 2 Select key accesses the character in the next level, that is, when in level 1, it accesses the character in level 2, and when in level 2, it accesses the character in level 1. The examples below show two possible implementations of the capital lock and level 2 lock functions.

Example: Pressing the key at position E-09 of the keyboard shown earlier produces the following

Supporting capital lock or level 2 lock function
9 ç Capital lock off Capital lock on
Level 2 Select off ç Ç
Level 2 Select on 9 9

Example: When you press the A key at position D-01 of the keyboard shown earlier, the following occurs:

Supporting Capital Lock or Level 2 Lock Function
A Capital Lock off Capital Lock on
Level 2 Select off a A
Level 2 Select on A A or a

Guideline E4


Implement within each keyboard group a Capital Lock function or a Level 2 Lock function depending on the requirement.


Users who are familiar with the Capital Lock key on the IBM PC USA keyboard appreciate the convenience that the key offers when entering a combination of uppercase letters and numbers. However, such convenience is not possible for keyboards such as the one shown earlier that have numeric digits on level 2.

Example: The digits 0 through 9 on the French keyboard are in level 2. Entering a string such as M3C1H7 is much quicker with the Level 2 Lock than with the Capital Lock function.