a keyboard having fewer keys than the characters available utilizes linked sequences of keystrokes in generation of some characters . other characters may be produced with one keystroke . the difference between linked keystrokes and independent keystrokes both made in sequence is determined by either the length of the interval between keystrokes or use of a delimiting key . a threshold level for the interval between keystrokes which decides whether two sequential keystrokes are linked or not may be set by the user or may be automatically determined with the use of an adaptive predictive algorithm . it is generally suggested that pairs of keys be linked , particularly adjacent pairs of keys in a fixed configuration , and that the characters generated by either a single keystroke of a given key or the characters generated by two linked keystrokes be represented upon the keyboard in a disposition which facilitates intuitive learning of the keyboard . the characters ‘ a ’ and ‘ b ’ might both be represented between the keys identified as ‘ 1 ’ and ‘ 2 ’ with the ‘ a ’ adjacent the ‘ 1 ’ and the ‘ b ’ adjacent the ‘ 2 ’ connoting that the linked keystrokes 1 - 2 generate the character ‘ a ’, the linked keystrokes 2 - 1 generate the character ‘ b ’ and independent keystrokes 1 and 2 each generate the characters ‘ 1 ’ and ‘ 2 ’ respectively . the keys may be identified and arranged in a fixed configuration in any manner desired . a hexagonal pattern with keys identified by a simplified morse code using ·, -, ··, --, ·-, and -· is specifically suggested for use by those having a physical disability .