High Frequency Alphabet Layout for On-Screen Scanning

Although some students best option for accessing an on-screen keyboard on a computer or communication device is though scanning, it can be very slow and inefficient. To make scanning more efficient, it is important that careful consideration is given to the scanning pattern and the keyboard layout. There are several different types of scanning modes and keyboard layouts.

Scanning Patterns

Some of the most common scanning patterns are as follows:

Linear Scanning. In this type of scanning, each letter is highlighted in sequential order from left to right. First,  first letter on the far left of the top row is highlighted. Next, that letter is no longer highlighted and the next letter beside it is highlighted. One by one, each letter is highlighted and this continues until the end of the row and then starts again on the next row. After each letter has been highlighted on every row, the scanning is usually programmed to begin again on the first row. When the desired letter is highlighted, the student indicates that it is his or her choice by activating a switch. Linear scanning is good for beginning scanners. However, it is very slow and can become frustrating. For example, if the student misses the desired letter, he or she will have to wait for it to finish scanning the rest of the 26 letters and begin again.

Circular Scanning. In this type of scanning, letters are arranged in a circle. Like linear scanning, it selects one at a time.

Row-column Scanning. In this type of scanning, the entire first row is highlighted. If it is not selected, then the highlight goes out and the second row is highlighted. Each row is highlighted until the student selects the row by activating a switch.  Once the row has been selected, then each letter in the row is individually highlighted until the student selects the letter. Row-column scanning has the advantage over linear scanning of speed. Students are able to access the letter they want much faster.

Group Item Scanning. In this type of scanning, a group of letters are highlighted first. For example, the top half of the alphabet may be highlighted (consisting of several rows) and then the bottom half. After the group is selected, it may progress to a row-column type of scan. This is even faster than row-column scanning.

Keyboard Layout Patterns

Although scanning patterns will be an important consideration, equally important is how the keyboard will be arranged. This is important due to the amount of time it will take for the device to scan to the desired letter. Some students will become frustrated if it takes too long to get to the letter they desire.

There are several different types of keyboard arrangements.

Alphabet layout. In an alphabet layout pattern, the on-screen keyboard is arranged in order of the alphabet (a, b, c, d...). Although this may initially seem like a good idea for younger students, it will become frustrating for students who are waiting for the scanning to highlight the parts of the alphabet that are far from the top row (or far from the left side for those doing row-column or group scanning).

QWERTY layout. A QWERTY layout is the standard keyboard layout found on most keyboards. QWERTY keyboards were designed with letters in an order designed to result in a slower typing speed. Typing had to be slowed down since the keys would get stuck in the old fashioned typewriters when the person hit the keys in too fast a manner. If the student is using scanning and an on-screen keyboard, then it is assumed that he is not using a standard keyboard. Typically the QWERTY layout is not used for on-screen scanning. For students who initially learned using a QWERTY layout, they may be changed to a high frequency alphabet layout to increase typing speed.

High Frequency Scanning Alphabet Layout. In a high frequency alphabet keyboard layout, the letters are arranged according to frequency of use. In a row-column scanning format, the keys are arranged with the most frequently used letters on the top row and along the left side. The least used letters are found near the bottom right corner. By having the layout arranged by frequency of using the letters, the student can get to the letters most frequently used in the English language the quickest.

High frequency scanning alphabet keyboard layouts are the layouts of choice when the student must scan. Most companies that sell programs with alphabet layouts for scanning also include several high frequency alphabet layouts. Although they can differ, they are all built on the premise that the most frequent letters (e.g., a, e, t, n) are the fastest to activate and the least used letters (e.g., z, j, x, z) take the longest to select. Most programs will allow the user or teacher to program in their own alphabet layout.

The example below was modified from a high frequency scanning alphabet layout from EZ Keys. It provides the vowels on the top row which can be helpful for beginning spellers. Notice how the most commonly used letters are in the left top corner and progress to the least commonly used ones in the bottom right corner. This layout has been successfully used with an elementary school student with severe physical disabilities using row-column scanning for beginning writing assignments.