Text and Images Copyright (C) 2006, 2007 Mike Sebastian

Sub-Twenty Dollar Graphing Calculators

In June, 2006, graphing calculators for under $20 started being sold. The first of these inexpensive graphing calculators I personally saw was sold by Walmart as the Durabrand 828. Since that time, several additional inexpensive graphing calculators have hit the market.

Of those calculators I have personally evaluated, they appear to be imperfect clones of the Casio fx-6300G. These calculators have the same functions and the same amount of memory. The owners manuals look like they were plagiarized from the fx-6300G manual. However, they have a smaller graphing display region than the fx-6300G and bugs not present in the fx-6300G.

From a hardware perspective I have seen three variants of these calculators.

The oldest variant appears to utilize the chip used in the Citizen SRP-320G. This variant has the same forensics result (9.0000296195) and the same arcsin bug first observed in the SRP-320G. The calculator does not compute arcsin in degrees, even when in degrees mode, as part of a program or as part of a formula such as the forensics formula. It will also not accept graphing functions in a program. The graphing region of this calculator is 35 by 23 pixels. This variant is found in the SC-828 version of the Durabrand 828.

The second variant has the forensics result and bugs of the first variant, but has a slightly smaller graphing region in the display of 33 by 23 pixels, instead of 35 by 23 pixels (see pictures below). This variant is found in the Sentry CA756.

The third variant corrects the bugs found in the first two versions, and produces a different forensics result (8.999999998078897). This variant has the larger 35 by 23 pixel graphing region. This variant also lacks the ability to adjust display contrast (despite what the MODE reference table printed on the front of the calculator indicates). This variant is found in the SC-1376 version of the Durabrand 828 and the Corner Office ATC-139.

The 35 by 23 pixel graphing region utilized by the Durabrand 828 and Corner Office ATC-139. The 33 by 23 pixel graphing region utilized by the Sentry CA756. An approximate 1.4 high by 1.0 wide aspect ratio for each pixel makes the graphing region appear square.

The graphing region of the display is composed of two separate areas. The upper area is 7 rows by 33 columns. The lower region is 16 rows by either 33 or 35 columns.

Brand Name & Model Overall Rating Display Keyboard External Quality Internal Quality Purchase Comments
Durabrand 828 good good 35x23 pixel, 11 characters, 3 numeric good+, hard plastic keys good good 6/5/06 Walmart $19.86 Two functionally distinct versions are being sold. For more details about the two versions, check out the The Great Durabrand Mystery.
Corner Office ATC-139 fair+ good 35x23 pixel, 11 characters, 3 numeric good+, hard plastic keys good- good 7/30/07 Walgreens $19.99 on sale. Regular price $29.99. Black keyboard legends on dark gray case virtually unreadable. Colors of MODE, SHIFT and ALPHA keys do not correspond to colors of keyboard legends.
Sentry CA756 good+ good 33x23 pixel, 11 characters, 3 numeric good+, hard plastic keys good+ good 8/13/07 Big Lots! $16.00. Keyboard legend colors provide very good contrast - easy to read.


Last updated September 3, 2007